Transmission method, reception method, transmission apparatus, and reception apparatus

ABSTRACT

A transmission method includes: generating a frame for transfer which stores one or more first internet protocol (IP) packets storing content, and one or more second IP packets each including reference clock information which indicates a time for a playback of the content; and transmitting the generated frame through broadcasting. In the generating, header compression is performed on the one or more first IP packets and the header compression is not performed on the one or more second IP packets.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. continuation application of PCT InternationalPatent Application Number PCT/JP2015/005957 filed on Dec. 1, 2015,claiming the benefit of priority of Japanese Patent Application Number2015-220646 filed on Nov. 10, 2015, and U.S. Provisional Application No.62/090,003 filed on Dec. 10, 2014, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a transmission method, a receptionmethod, a transmission apparatus, and a reception apparatus.

2. Description of the Related Art

An MMT (MPEG Media Transport) scheme (refer to NPL 1: Informationtechnology-High efficiency coding and media delivery in heterogeneousenvironments-Part 1: MPEG media transport (MMT), ISO/IEC DIS 23008-1) isa multiplexing scheme for multiplexing and packetizing content such asvideo and voice and for transmitting the content through one or moretransfer channels such as broadcast and broadband. When the MMT schemeis applied to broadcasting systems, reference clock information of atransmission apparatus is transmitted to a reception apparatus, and thereception apparatus generates a system clock in the reception apparatusbased on the reference clock information.

SUMMARY

It is desirable that such reception apparatus can shorten the processingdelay in channel selection.

The non-limiting exemplary embodiments of the present disclosure providea transmission method, a reception method, a transmission apparatus, ora reception apparatus, with which the processing delay in channelselection can be shortened.

The transmission method according to one aspect of the presentdisclosure includes: generating a frame for transfer in which one ormore first internet protocol (IP) packets and one or more second IPpackets are stored, the one or more first IP packets storing content,and each of the one or more second IP packets including reference clockinformation which indicates a time for playing back the content; andtransmitting the generated frame through broadcasting. In thegenerating, header compression is performed on the one or more first IPpackets and the header compression is not performed on the one or moresecond IP packets.

In addition, the reception method according to one aspect of the presentdisclosure includes: receiving, through broadcasting, a frame fortransfer in which one or more internet protocol (IP) packets are stored,the one or more IP packets storing content and including: one or morefirst IP packets whose headers have been compressed; and one or moresecond IP packets whose headers have not been compressed, each of theone or more second IP packets including reference clock informationwhich indicates a time for playing back the content; determining whethereach of the one or more IP packets that are received is the first IPpacket or the second IP packet based on whether or not a header of theIP packet has been compressed; and playing back the content stored inthe one or more first IP packets, using the reference clock informationstored in the each of the one or more second IP packets, based on aresult of the determination.

Note that these general or specific aspects may be implemented using asystem, an apparatus, a method, an integrated circuit, a computerprogram, or a computer-readable recording medium such as a CD-ROM. Also,these general or specific aspects may be implemented using anycombination of a system, an apparatus, a method, an integrated circuit,a computer program, and a recording medium.

The present disclosure provides a transmission method, a receptionmethod, a transmission apparatus, or a reception apparatus, with whichthe processing delay in channel selection can be shortened.

Further advantages and effects according to one aspect of the presentdisclosure are made apparent from the description and the drawings.Although such advantages and/or effects are respectively provided by thefeatures described in several exemplary embodiments, and the descriptionand the drawings, all of the advantages and effects need not necessarilybe provided in order to obtain one or more of the same features as thosedescribed therein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a protocol stack for performingtransfer using an MMT scheme and an advanced BS transfer scheme;

FIG. 2 is a diagram illustrating data structure of a TLV packet;

FIG. 3 is a block diagram illustrating a basic configuration of areception apparatus;

FIG. 4 is a block diagram illustrating a functional configuration of thereception apparatus when reference clock information is stored in anextension field of an MMT packet header;

FIG. 5 is a diagram illustrating an acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the extension field of the MMTpacket header;

FIG. 6 is a block diagram illustrating the functional configuration ofthe reception apparatus when the reference clock information is storedin control information;

FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the control information;

FIG. 8 is a block diagram illustrating the configuration of thereception apparatus when the reference clock information is stored inthe TLV packet;

FIG. 9 is a diagram illustrating an example in which a long-format NTPis stored in the TLV packet;

FIG. 10 is a diagram illustrating the acquisition flow of the referenceclock information performed by the reception apparatus when thereference clock information is stored in the TLV packet;

FIG. 11 is a diagram illustrating structure in which the reference clockinformation is appended immediately before an IP packet header;

FIG. 12 is a diagram illustrating structure in which the reference clockinformation is appended immediately before the TLV packet;

FIG. 13 is a diagram illustrating structure of a transfer slot;

FIG. 14 is a diagram illustrating structure of a slot header of thetransfer slot;

FIG. 15 is a diagram illustrating an example in which a flag is storedin an undefined area of the slot header;

FIG. 16 is a diagram illustrating structure of TMCC control informationunder a transfer scheme for advanced broadband satellite digitalbroadcast;

FIG. 17 is a diagram illustrating stream classification/relative streaminformation of the TMCC control information;

FIG. 18 is a diagram illustrating an example in which the referenceclock information is stored in an undefined field of the slot header;

FIG. 19 is a block diagram illustrating the functional configuration ofthe reception apparatus when information indicating that the referenceclock information is contained within the slot header is stored in TMCCcontrol information;

FIG. 20 is a diagram illustrating the acquisition flow of the referenceclock information when the information indicating that the referenceclock information is contained in the slot header is stored in the TMCCcontrol information;

FIG. 21 is a diagram illustrating a flow of extracting a bit string at aspecific position from the IP packet or compressed IP packet;

FIGS. 22A and 22B are diagrams respectively illustrating an example of astructure of TMCC extension information, and an example of theconventionally proposed bit assignment method when the extension area isused as a payload;

FIG. 23 is a diagram illustrating an example of data structure of anextension area in which an extension classification classified in thisway is used;

FIGS. 24A and 24B are diagrams respectively illustrating first andsecond examples of syntax when the extension classification is used;

FIG. 25 is a block diagram illustrating a functional configuration of areception apparatus according to a second exemplary embodiment;

FIG. 26 is a diagram illustrating an operation flow of the receptionapparatus according to the second exemplary embodiment;

FIG. 27 is a diagram schematically illustrating an example in which thereference clock information is stored in each of a plurality of layers;

FIG. 28 is a diagram schematically illustrating an example in which aplurality of pieces of the reference clock information is stored in onelayer;

FIG. 29 is a block diagram for describing an example in which data ofdifferent broadcasting stations is stored in separate streams;

FIG. 30 is a diagram for describing a transmission method of differenceinformation;

FIG. 31 is a diagram for describing a variation of the transmissionmethod of the difference information;

FIG. 32 is a block diagram illustrating a functional configuration of areception apparatus according to a third exemplary embodiment;

FIG. 33 is a diagram illustrating an operation flow of the receptionapparatus according to the third exemplary embodiment;

FIG. 34 is a diagram illustrating another operation flow of thereception apparatus according to the third exemplary embodiment;

FIG. 35 is a block diagram illustrating a functional configuration of atransmission apparatus;

FIG. 36 is a diagram illustrating an operation flow of the transmissionapparatus;

FIG. 37 is a block diagram of a reception apparatus according to afourth exemplary embodiment;

FIG. 38 is a diagram illustrating timing of a main signal and referenceclock information according to the fourth exemplary embodiment;

FIG. 39 is a diagram illustrating an operation flow in a decoderaccording to the fourth exemplary embodiment;

FIG. 40 is a diagram illustrating an operation flow in the receptionapparatus according to the fourth exemplary embodiment;

FIG. 41 is a diagram illustrating an operation flow in an upper layeraccording to the fourth exemplary embodiment;

FIG. 42 is a diagram illustrating an operation flow of a decodingapparatus according to the fourth exemplary embodiment;

FIG. 43 is a diagram illustrating an operation flow of a demultiplexingapparatus according to the fourth exemplary embodiment;

FIG. 44 shows a structure of a transfer frame according to a fifthexemplary embodiment;

FIG. 45 shows a structure of the transfer frame according to the fifthexemplary embodiment;

FIG. 46 shows a structure of the transfer frame according to the fifthexemplary embodiment;

FIG. 47 is a diagram illustrating a transmission method according to thefifth exemplary embodiment;

FIG. 48 is a diagram illustrating an operation flow in a transmissionapparatus according to the fifth exemplary embodiment;

FIG. 49 is a diagram showing a structure of the transfer frame accordingto the fifth exemplary embodiment;

FIG. 50 is diagram for illustrating header compression according to asixth exemplary embodiment;

FIG. 51 is a diagram for illustrating the header compression accordingto the sixth exemplary embodiment;

FIG. 52 is a diagram showing an operation flow of the receptionapparatus according to the sixth exemplary embodiment;

FIG. 53 is a diagram showing an operation flow of the receptionapparatus according to the sixth exemplary embodiment;

FIG. 54 is a block diagram showing the transmission apparatus accordingto the sixth exemplary embodiment;

FIG. 55 is a diagram showing an operation flow of the transmissionapparatus according to the sixth exemplary embodiment;

FIG. 56 is a block diagram showing the reception apparatus according tothe sixth exemplary embodiment; and

FIG. 57 is a diagram showing an operation flow of the receptionapparatus according to the sixth exemplary embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS (Underlying Knowledge FormingBasis of the Present Disclosure)

The present disclosure relates to a method and apparatus fortransmitting reference clock information from a transmission side,receiving the reference clock information on a reception side, andgenerating (reproduction: playback) a reference clock in a hybriddelivery system using an MMT scheme which is under standardization byMPEG (Moving Picture Expert Group).

The MMT scheme is a multiplexing scheme for multiplexing and packetizingvideo and audio to transmit the video and audio via one or more transferchannels such as broadcast and broadband.

When the MMT scheme is applied to a broadcasting system, the referenceclock on the transmission side is synchronized with an NTP (Network TimeProtocol) prescribed by IETF RFC (Internet Engineering Task ForceRequest for Comments) 5905, and based on the reference clock, a timestamp such as PTS (Presentation Time Stamp) and DTS (Decode Time Stamp)is added to a medium. Furthermore, the reference clock information onthe transmission side is transmitted to the reception side, and areception apparatus generates the reference clock (hereinafter alsoreferred to as a system clock) in the reception apparatus based on thereference clock information.

In the broadcasting system, a 64-bit long-format NTP capable ofindicating absolute time is preferably used as the reference clockinformation. However, although the conventional MMT scheme prescribesstoring a 32-bit short-format NTP in an MMT packet header andtransferring the 32-bit short-format NTP, the conventional MMT schemedoes not prescribe transferring the long-format NTP, and a receiverdevice side cannot acquire high-precision reference clock information.

In contrast, it is possible to define the long-format NTP as controlinformation, such as a message, a table, or a descriptor, and to appendthe MMT packet header to the control information for transfer. In thiscase, the MMT packet is, for example, stored in an IP packet, and istransferred through a broadcast transfer channel or a broadband transferchannel.

When the MMT packet is transferred using an advanced BS transfer scheme(transmission system for advanced wide band digital satellitebroadcasting) prescribed by the ARIB standard, after encapsulation ofthe MMT packet into the IP packet and encapsulation of the IP packetinto a TLV (Type Length Value) packet, the MMT packet is stored in atransfer slot prescribed by the advanced BS transfer scheme.

When extracting a desired IP data flow from a TLV stream, the receptionapparatus performs filtering of IP data flows or filtering of IP packetsor UDP packets. In addition, when filtering the IP data flows, thereception apparatus needs to specify the IP data flow of a desiredservice and identify the packets that belong to the desired IP dataflow.

However, the reception apparatus can identify the packets that belong tothe desired IP data flow only after the reception of a full header. Thismight delay the processing until the reception apparatus firstlyreceives a full header, and thus the processing delay in channelselection gets longer in some cases. Moreover, in the case where thetransmission intervals of the full headers are long, the processingdelay in channel selection gets even longer.

The transmission method according to one aspect of the presentdisclosure includes: generating a frame for transfer in which one ormore first internet protocol (IP) packets and one or more second IPpackets are stored, the one or more first IP packets storing content,and each of the one or more second IP packets including reference clockinformation which indicates a time for playing back the content; andtransmitting the generated frame through broadcasting. In thegenerating, header compression is performed on the one or more first IPpackets and the header compression is not performed on the one or moresecond IP packets.

This enables the reception apparatus to filter the IP data flows basedon whether or not the header compression has been performed. Thus, it ispossible to shorten the processing delay in channel selection.

For example, in the generating, the header compression may include: (i)attaching, to a part of the one or more first IP packets, a full headerwhich includes specification information for specifying an IP data flowto which the one or more first IP packets belong; and (ii) attaching, toa first IP packet other than the part of the one or more first IPpackets, a compressed header which does not include the specificationinformation.

For example, the reference clock information may comply with a networktime protocol (NTP).

For example, the content may be stored in an MPEG media transport (MMT)packet in each of the one or more first IP packets.

For example, the frame may include one or more second transfer units,each having a fixed length, each of the one or more second transferunits may include one or more first transfer units, and each of the oneor more first transfer units may include one of the one or more first IPpackets; and the one or more second IP packets.

For example, each of the one or more first transfer units may be a typelength value (TLV) packet, each of the one or more second transfer unitsmay be a slot defined under a transmission system for advanced wide bandsatellite digital broadcasting, and the frame may be a transfer slotdefined under the transmission system for advanced wide band satellitedigital broadcasting.

The reception method according to one aspect of the preset disclosureincludes: receiving, through broadcasting, a frame for transfer in whichone or more internet protocol (IP) packets are stored, the one or moreIP packets storing content and including: one or more first IP packetswhose headers have been compressed; and one or more second IP packetswhose headers have not been compressed, each of the one or more secondIP packets including reference clock information which indicates a timefor playing back the content; determining whether each of the one ormore IP packets that are received is the first IP packet or the secondIP packet based on whether or not a header of the IP packet has beencompressed; and playing back the content stored in the one or more firstIP packets, using the reference clock information stored in the each ofthe one or more second IP packets, based on a result of thedetermination.

This enables the reception apparatus to filter the IP data flows basedon whether or not the header compression has been performed. Thus, it ispossible to shorten the processing delay in channel selection.

For example, the header compression may include: (i) attaching, to apart of the one or more first IP packets, a full header which includesspecification information for specifying an IP data flow to which theone or more first IP packets belong; and (ii) attaching, to a first IPpacket other than the part of the one or more first IP packets, acompressed header which does not include the specification information.

For example, the reference clock information may comply with a networktime protocol (NTP).

For example, the content may be stored in an MPEG media transport (MMT)packet in each of the one or more first IP packets.

For example, the frame may include one or more second transfer units,each having a fixed length, each of the one or more second transferunits may include one or more first transfer units, and each of the oneor more first transfer units may include one of the one or more first IPpackets; and the one or more second IP packets.

For example, each of the one or more first transfer units may be a typelength value (TLV) packet, each of the one or more second transfer unitsmay be a slot defined under a transmission system for advanced wide bandsatellite digital broadcasting, and the frame may be a transfer slotdefined under the transmission system for advanced wide band satellitedigital broadcasting.

The transmission apparatus according to one aspect of the presentdisclosure includes: a generator which generates a frame for transfer inwhich one or more first internet protocol (IP) packets and one or moresecond IP packets are stored, the one or more first IP packets storingcontent, and each of the one or more second IP packets includingreference clock information which indicates a time for playing back thecontent; and a transmitter which transmits the generated frame throughbroadcasting. The generator performs header compression on the one ormore first IP packets and does not perform the header compression on theone or more second IP packets.

This enables the reception apparatus to filter the IP data flows basedon whether or not the header compression has been performed. Thus, it ispossible to shorten the processing delay in channel selection.

The reception apparatus according to one aspect of the presentdisclosure includes: a receiver which receives, through broadcasting, aframe for transfer in which one or more internet protocol (IP) packetsare stored, the one or more IP packets storing content and including:one or more first IP packets whose headers have been compressed; and oneor more second IP packets whose headers have not been compressed, eachof the one or more second IP packets including reference clockinformation which indicates a time for playing back the content; adeterminer which determines whether each of the one or more IP packetsthat are received is the first IP packet or the second IP packet basedon whether or not a header of the IP packet has been compressed; and aplayback unit which plays back the content stored in the one or morefirst IP packets, using the reference clock information stored in theeach of the one or more second IP packets, based on a result of thedetermination.

This enables the reception apparatus to filter the IP data flows basedon whether or not the header compression has been performed. Thus, it ispossible to shorten the processing delay in channel selection.

Exemplary embodiments will be specifically described below withreference to the drawings.

In addition, the exemplary embodiments described below are each acomprehensive or specific example. Numerical values, shapes, materials,components, placement positions and connection modes of the components,steps and a step order described in the following exemplary embodimentsare exemplary, and by no means limit the present disclosure. Further,components which are not recited in the independent claims representingthe uppermost generic concepts among components in the followingexemplary embodiments will be described as arbitrary components.

First Exemplary Embodiment [Basic Configuration of an MMT Scheme]

First, a basic configuration of an MMT scheme will be described. FIG. 1illustrates a protocol stack diagram for performing transfer using theMMT scheme and an advanced BS transfer scheme.

Under the MMT scheme, information such as video and audio is stored in aplurality MPUs (Media Presentation Units) and a plurality of MFUs (MediaFragment Units), and an MMT packet header is added forMMT-packetization.

Meanwhile, under the MMT scheme, the MMT packet header is also added tocontrol information such as an MMT message for MMT-packetization. TheMMT packet header is provided with a field that stores a 32-bitshort-format NTP, and this field can be used for QoS control ofcommunication lines, etc.

MMT-packetized data is encapsulated into an IP packet having a UDPheader or IP header. At this time, in the IP header or UDP header, whena set of packets with an identical source IP address, destination IPaddress, source port number, destination port number, and protocolclassification is an IP data flow, headers of the plurality of IPpackets contained in one IP data flow are redundant. Therefore, headercompression of some IP packets is performed in one IP data flow.

Next, a TLV packet will be described in detail. FIG. 2 is a diagramillustrating data structure of the TLV packet.

The TLV packet stores an IPv4 packet, IPv6 packet, compressed IP packet,NULL packet, and transfer control signal, as illustrated in FIG. 2.These pieces of information are identified using an 8-bit data type.Examples of the transfer control signal include an AMT (Address MapTable) and NIT (Network Information Table). Also, in the TLV packet, adata length (byte unit) is indicated using a 16-bit field, and a valueof data is stored after the data length. Since there is 1-byte headerinformation before the data type (not illustrated in FIG. 2), the TLVpacket has a total of 4-byte header area.

The TLV packet is mapped to a transfer slot under the advanced BStransfer scheme. Pointer/slot information that indicates a head positionof a first packet and a tail position of a last packet which arecontained in every slot are stored in TMCC (Transmission andMultiplexing Configuration Control) control information (controlsignal).

Next, a configuration of a reception apparatus when the MMT packet istransferred by using the advanced BS transfer scheme will be described.FIG. 3 is a block diagram illustrating the basic configuration of thereception apparatus. Note that the configuration of the receptionapparatus of FIG. 3 is simplified. More specific configuration will bedescribed later individually according to a manner in which referenceclock information is stored.

Reception apparatus 20 includes receiver 10, decoder 11, TLVdemultiplexer (DEMUX) 12, IP demultiplexer (DEMUX) 13, and MMTdemultiplexer (DEMUX) 14.

Receiver 10 receives transfer channel coded data.

Decoder 11 decodes the transfer channel coded data received by receiver10, applies error correction and the like, and extracts the TMCC controlinformation and TLV data. The TLV data extracted by decoder 11 undergoesDEMUX processing by TLV demultiplexer 12.

The DEMUX process performed by TLV demultiplexer 12 differs according tothe data type. For example, when the data type is a compressed IPpacket, TLV demultiplexer 12 performs processes such as decompressingthe compressed header and passing the header to an IP layer.

IP demultiplexer 13 performs processing such as header analysis of an IPpacket or UDP packet, and extracts the MMT packet for each IP data flow.

MMT demultiplexer 14 performs a filtering process (MMT packet filtering)based on a packet ID stored in the MMT packet header.

[Method for Storing the Reference Clock Information in the MMT Packet]

Under the MMT scheme described with reference to FIG. 1 to FIG. 3described above, although the 32-bit short-format NTP can be stored inthe MMT packet header and transferred, there exists no method fortransferring a long-format NTP.

Hereinafter, a method for storing the reference clock information in theMMT packet will be described. First, the method for storing thereference clock information within the MMT packet will be described.

When a descriptor, a table, or a message for storing the reference clockinformation is defined and stored in the MMT packet as controlinformation, an identifier indicating that the control information isthe descriptor, table, or message indicating the reference clockinformation is indicated within the control information. Then, thecontrol information is stored in the MMT packet on a transmission side.

This allows reception apparatus 20 to identify the reference clockinformation based on the identifier. Note that the reference clockinformation may be stored in the MMT packet by using existingdescriptors (for example, CRI_descriptor( ) etc.).

Next, a method for storing the reference clock information in the MMTpacket header will be described.

For example, there is a method for storing the reference clockinformation by using a header_extension field (hereinafter referred toas an extension field). The extension field becomes effective when anextension_flag of the MMT packet header is set to ‘1’.

There is such a method that an extension field type indicating dataclassification of data to be stored in the extension field is stored inthe extension field, information indicating that the data is thereference clock information (for example, a 64-bit long-format NTP) isstored in the extension field type, and the reference clock informationis stored in the extension field.

In this case, when the header_extension_flag of the MMT packet header is‘1’, reception apparatus 20 refers to the extension field of the MMTpacket. When the extension field type indicates that the data is thereference clock information, the reference clock information isextracted and a clock is reproduced.

Note that the reference clock information may be stored in an existingheader field. In addition, when there is an unused field or when thereis a field unnecessary for broadcast, the reference clock informationmay be stored in these fields.

In addition, the reference clock information may be stored by using theexisting field and the extension field together. For example, theexisting 32-bit short-format NTP field and the extension field may beused together.

In order to maintain compatibility with the existing field, of the64-bit long-format NTP, only a 32-bit section corresponding to ashort-format format may be stored in the existing field, and remaining32 bits may be stored in the extension field.

Here, the reference clock information is, for example, time when a headbit of the MMT packet in which the reference clock information is storedpasses a predetermined position (for example, when the head bit isoutput from a specific component of a transmission apparatus). However,the reference clock information may be time when a bit of anotherposition passes the predetermined position.

When the reference clock information is stored in the MMT packet as thecontrol information, the MMT packet containing the control informationis transmitted at predetermined transmission intervals.

When the reference clock information is stored in the extension field ofthe MMT packet, the reference clock information is stored in theextension field of a predetermined MMT packet header. Specifically, forexample, at least one or more pieces of the reference clock informationare stored in the header extension fields of the MMT packets atintervals of 100 ms.

Note that, when the reference clock information is stored in the MMTpacket, the packet ID of the MMT packet that stores the reference clockinformation is stored in program information. Reception apparatus 20analyzes the program information and acquires the MMT packet in whichthe reference clock information is stored. At this time, the packet IDof the MMT packet in which the reference clock information is stored maybe prescribed in advance as a fixed value. This allows receptionapparatus 20 to acquire the reference clock information withoutanalyzing the program information.

[Operation Flow when the Reference Clock Information is Stored in theMMT Packet]

Next, an operation flow when the reference clock information is storedin the MMT packet (acquisition flow of the reference clock information)will be described.

First, the following describes the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader. FIG. 4 is a block diagram illustrating a functionalconfiguration of reception apparatus 20 when the reference clockinformation is stored in the extension field of the MMT packet header.FIG. 5 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the extension field of the MMT packetheader.

As illustrated in FIG. 4, when the reference clock information is storedin the extension field of the MMT packet header, reference clockinformation extractor 15 (an example of the extractor) is providedwithin MMT demultiplexer 14, and reference clock generator 16 (anexample of the generator) is provided downstream of MMT demultiplexer14.

In the flow of FIG. 5, decoder 11 of reception apparatus 20 decodes thetransfer channel coded data received by receiver 10 (S101), and extractsthe TLV packet from the transfer slot (S102).

Next, TLV demultiplexer 12 performs DEMUX on the extracted TLV packet toextract the IP packet (S103). At this time, the header of the compressedIP packet is reproduced.

Next, IP demultiplexer 13 performs DEMUX on the IP packet, acquires thespecified IP data flow, and extracts the MMT packet (S104).

Next, MMT demultiplexer 14 analyzes the header of the MMT packet, anddetermines whether the extension field is used and whether the referenceclock information is in the extension field (S106). When there is noreference clock information in the extension field (No in S106), theprocess ends.

On the other hand, when the determination is made such that thereference clock information is in the extension field (Yes in S106),reference clock information extractor 15 extracts the reference clockinformation from the extension field (S107). Then, reference clockgenerator 16 generates the system clock based on the extracted referenceclock information (S108). The system clock is, in other words, a clockfor playing back content.

Next, the acquisition flow of the reference clock information byreception apparatus 20 when the reference clock information is stored inthe control information will be described. FIG. 6 is a block diagramillustrating the functional configuration of reception apparatus 20 whenthe reference clock information is stored in the control information.FIG. 7 is a diagram illustrating the acquisition flow of the referenceclock information performed by reception apparatus 20 when the referenceclock information is stored in the control information.

As illustrated in FIG. 6, when the reference clock information is storedin the control information, reference clock information extractor 15 isdisposed downstream of MMT demultiplexer 14.

In the flow of FIG. 7, the processes of step S111 to step S114 areidentical to the flow of step S101 to step S104 described in FIG. 5.

Subsequently to step S114, MMT demultiplexer 14 acquires the packet IDof the packet containing the reference clock information from theprogram information (S115), and acquires the MMT packet of the packet ID(S116). Subsequently, reference clock information extractor 15 extractsthe reference clock information from the control signal contained in theextracted MMT packet (S117), and reference clock generator 16 generatesthe system clock based on the extracted reference clock information(S118).

[Method for Storing the Reference Clock Information in the TLV Packet]

As described in FIG. 5 and FIG. 7, when the reference clock informationis stored in the MMT packet, in order to obtain the reference clockinformation on the reception side, reception apparatus 20 extracts theTLV packet from the transfer slot, and extracts the IP packet from theTLV packet. Furthermore, reception apparatus 20 extracts the MMT packetfrom the IP packet, and further extracts the reference clock informationfrom the header or a payload of the MMT packet. Thus, when the referenceclock information is stored in the MMT packet, many processes arerequired for acquiring the reference clock information, and longer timeis required until the acquisition, in some cases.

Therefore, a method will be described for implementing a process ofadding a time stamp to a medium, such as video and audio, based on thereference clock, and a process of transferring the medium by using theMMT scheme, and for performing transfer of the reference clockinformation by using a lower layer, lower protocol, or lowermultiplexing scheme than the MMT layer.

First, a method for storing the reference clock information in the TLVpacket for transfer will be described. FIG. 8 is a block diagramillustrating the configuration of reception apparatus 20 when thereference clock information is stored in the TLV packet.

Reception apparatus 20 illustrated in FIG. 8 differs from receptionapparatus 20 of FIG. 4 and FIG. 6 in placement of reference clockinformation extractor 15 and reference clock generator 16. In addition,synchronizer 17 and decoding presenter 18 are also illustrated in FIG.8.

The TLV packet includes the 8-bit data type, 16-bit data length, and8*N-bit data, as illustrated in aforementioned FIG. 2. In addition,1-byte header which is not illustrated in FIG. 2 exists before the datatype, as described above. Here, the data type is specificallyprescribed, for example, as 0x01: IPv4 packet, 0x03: header-compressedIP packet, etc.

In order to store new data in the TLV packet, an undefined area of thedata type is used to prescribe the data type. In order to indicate thatthe reference clock information is stored in the TLV packet, the datatype describes that the data is the reference clock information.

Note that the data type may be prescribed for each kind of the referenceclock. For example, the data types that indicate the short-format NTP,long-format NTP, and PCR (Program Clock Reference) may be prescribedindividually. FIG. 9 is a diagram illustrating an example in which thelong-format NTP is stored in the TLV packet. The long-format NTP isstored in a data field.

In this case, reference clock information extractor 15 analyzes the datatype of TLV packet. When the reference clock information is stored,reference clock information extractor 15 analyzes the data length, andextracts the reference clock information from the data field.

Here, when the data length is uniquely determined by the data type,reference clock information extractor 15 may acquire the reference clockinformation without analyzing a data length field. For example, when thedata type indicates a 64-bit long low mat NTP, reference clockinformation extractor 15 may extract a section from (4 bytes+1 bit)-thbit to (4 bytes+64 bits)-th bit. Also, reference clock informationextractor 15 may extract only a desired bit from 64-bit data.

Next, the operation flow of reception apparatus 20 when the referenceclock information is stored in the TLV packet (acquisition flow of thereference clock information) will be described with reference to FIG.10. FIG. 10 is a diagram illustrating the acquisition flow of thereference clock information performed by reception apparatus 20 when thereference clock information is stored in the TLV packet.

In the flow of FIG. 10, first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S121), and extracts the TLV packetfrom the transfer slot (S122).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S123),and determines whether the data type is the reference clock information(S124). When the data type is the reference clock (Yes in S124),reference clock information extractor 15 extracts the reference clockinformation from the data field of the TLV packet (S125). Then,reference clock generator 16 generates the system clock based on thereference clock information (S126). On the other hand, when the datatype is not the reference clock information, (No in S124), theacquisition flow of the reference clock information ends.

In addition, in an unillustrated flow, IP demultiplexer 13 extracts theIP packet according to the data type. Then, the IP DEMUX process and MMTDEMUX process are performed on the extracted IP packet, and the MMTpacket is extracted. Furthermore, synchronizer 17 outputs video data todecoding presenter 18 with timing with which the time stamp of the videodata contained in the extracted MMT packet coincides with the referenceclock generated in step S126. Decoding presenter 18 decodes and presentsthe video data.

In the transmission method described above, the type data of the TLVpacket indicates that the reference clock information is stored, and thereference clock information is stored in the data field of the TLVpacket. Thus, by storing and transmitting the reference clockinformation by using a lower layer or lower protocol than the MMT layer,the processes and time until reception apparatus 20 extracts thereference clock information can be reduced.

Also, since the reference clock information can be extracted andreproduced in a lower layer extending over the IP layers, the referenceclock information can be extracted by hardware implementation. This canreduce more influence of jitter or the like than extracting thereference clock information by software implementation, and makes itpossible to generate higher-precision reference clock.

Next, other methods for storing the reference clock information will bedescribed.

When the data length is uniquely determined according to the data typein the aforementioned flow of FIG. 10, the data length field does notneed to be transmitted. Here, when the data length field is nottransmitted, an identifier is stored indicating that the data lengthfield is data that is not transmitted.

Although the reference clock information is stored in the data field ofthe TLV packet according to the description of FIG. 10, the referenceclock information may be appended immediately before or after the TLVpacket. Also, the reference clock information may be appendedimmediately before or after data to be stored in the TLV packet. Inthese cases, a data type that allows specification of a position wherethe reference clock information is appended is added.

For example, FIG. 11 is a diagram illustrating structure in which thereference clock information is appended immediately before the IP packetheader. In this case, the data type indicates an IP packet withreference clock information. When the data type indicates an IP packetwith reference clock information, reception apparatus 20 (referenceclock information extractor 15) can acquire the reference clockinformation by extracting bits of a previously prescribed predeterminedlength of the reference clock information from a head of the data fieldof the TLV packet. At this time, the data length may specify the lengthof data that includes the length of the reference clock information, andmay specify the length that does not include the length of the referenceclock information. When the data length specifies the length of datathat includes the length of the reference clock information, receptionapparatus 20 (reference clock information extractor 15) acquires data ofa length obtained by subtracting the length of the reference clockinformation from the data length from immediately after the referenceclock information. When the data length specifies the length of datathat does not include the length of the reference clock information,reception apparatus 20 (reference clock information extractor 15)acquires data of the length specified by the data length fromimmediately after the reference clock information.

In addition, FIG. 12 is a diagram illustrating structure in which thereference clock information is appended immediately before the TLVpacket. In this case, the data type is a conventional data type. Anidentifier indicating that the TLV packet is a TLV packet with referenceclock information is stored, for example, in a slot header of thetransfer slot or the TMCC control information. FIG. 13 is a diagramillustrating structure of the transfer slot, and FIG. 14 is a diagramillustrating structure of the slot header of the transfer slot.

As illustrated in FIG. 13, the transfer slot includes a plurality ofslots (120 slots of Slot #1 to Slot #120 in the example of FIG. 13). Abit number contained in each slot is a fixed bit number uniquelydetermined based on a coding rate of error correction, each of the slotshas a slot header and stores one or more TLV packets. Note that, asillustrated in FIG. 13, the TLV packet has a variable-length.

As illustrated in FIG. 14, in a head TLV instruction field (16 bits) ofthe slot header is stored a position of a head byte of a first TLVpacket within the slot indicated with a number of bytes from a slot headexcept the slot header. Remaining 160 bits of the slot header isundefined. The transfer slot includes 120 slots per frame as describedabove, and a modulation scheme is assigned to the slots in 5-slot unit.In addition, up to 16 streams can be transferred within one frame. Notethat the plurality of streams included in one transfer slot has, forexample, different pieces of content (or a company that provides thecontent) transferred by the streams. In addition, each stream includesone or more slots, and one slot does not extend over the plurality ofstreams.

When the identifier indicating that the TLV packet is a TLV packet withreference clock information is stored in the slot header, for example,information that allows specification of a position of the TLV packetwith reference clock information within the slot, kind of the referenceclock information, data length, and the like are stored by extending(using) an undefined field of the slot header.

Note that all pieces of information including the information thatallows specification of the position of the TLV packet with referenceclock information, kind of the reference clock information, and datalength do not need to be stored in the slot header. Only informationthat allows specification and reference of the TLV packet with referenceclock information needs to be indicated.

For example, when definition is made such that the reference clockinformation is a 64-bit long-format NTP, that only one TLV packet withreference clock information can be stored in one slot, and that the oneTLV packet with reference clock information is always the head TLVpacket, a flag may be stored in the undefined area of the slot header.FIG. 15 is a diagram illustrating an example in which the flag is storedin the undefined area of the slot header.

In the example of FIG. 15, the flag (described as “F” in the diagram)indicating whether the reference clock information is contained in theslot is stored in the undefined area of the slot header. With such aflag, reception apparatus 20 may determine that the head TLV packet is aTLV packet with reference clock information.

In addition, the identifier (information) indicating that the TLV packetis a TLV packet with reference clock information may be stored in theTMCC control information. FIG. 16 is a diagram illustrating structure ofthe TMCC control information under a transfer scheme for advancedbroadband satellite digital broadcast.

The information for specifying and referencing the TLV packet withreference clock information may be stored in extension informationwithin the TMCC control information illustrated in FIG. 16, and may bestored in another place within the TMCC control information. Forexample, stream classification/relative stream information in the TMCCcontrol information may be used as information for specifying andreferencing the TLV packet with reference clock information. FIG. 17 isa diagram illustrating the stream classification/relative streaminformation in the TMCC control information.

As illustrated in FIG. 17, in the stream classification/relative streaminformation, the stream classification of each of 16 streams isindicated in 8 bits. That is, 1-frame transfer slot can transfer up to16 (16-classification) streams. For example, the stream classificationof an MPEG2-TS stream is “00000000”, and the stream classification of aTLV stream is “00000010”. However, under the current circumstances, theclassifications of other streams are unassigned or undefined.

Therefore, when the stream classification of the TLV stream withreference clock is defined, for example, as “00000100” and when therelative stream is a TLV stream with reference clock, “00000100” isstored in the stream classification/relative stream information of theTMCC control information. Here, in the stream with the streamclassification of “00000100”, the TLV packet containing reference clockinformation is stored, for example, once per 5-slot unit which is a slotassignment unit, or once per frame unit.

In such structure, reception apparatus 20 analyzes the streamclassification/relative stream information in the TMCC controlinformation. When the stream classification is “00000100”, receptionapparatus 20 acquires the TLV packet with reference clock from the slotdetermined in advance.

A case is possible where the stream classification including downloadtype TLV packets and the stream classification including stream type TLVpackets, such as video and audio, are defined. In such a case, receptionapparatus 20 may determine that the reference clock information iscontained in the stream when the stream classification of the receivedstream is a stream type TLV packet. This is because the reference clockinformation is not usually used in reproduction of download type TLVpackets.

In addition, when the information for specifying and referencing the TLVpacket with reference clock information is stored in the extensioninformation of the TMCC control information, for example, informationfor each of the 16 relative streams is stored in the extension area ofthe TMCC control information.

Also, as illustrated in FIG. 18, an area into which the reference clockinformation is stored may be newly defined in the undefined field of theslot header. FIG. 18 is a diagram illustrating an example in which thereference clock information is stored in the undefined field of the slotheader.

Also, the reference clock information may be stored in a previouslydetermined slot, and information indicating that the reference clockinformation is contained may be stored within the slot header. Here, thepreviously determined slot is, for example, a head slot of the transferslot (Slot #1 in the example of FIG. 13), and the reference clockinformation stored in the IP packet may be contained in the head TLVpacket within this slot. Also, when the plurality of streams arecontained in the transfer slot, the previously determined slot may be,for example, a head slot of each stream contained in the transfer slot,and the reference clock information stored in the IP packet may becontained in the head TLV packet within this slot.

Also, information for specifying and referencing the slot headercontaining the reference clock information may be stored in the TMCCcontrol information. Note that the storage method of the information forspecifying and referencing the slot header containing the referenceclock information in the TMCC control information is similar to theaforementioned storage method of the information for specifying andreferencing the TLV packet with reference clock information, and thusdescription thereof will be omitted.

In this case, reception apparatus 20 analyzes the TMCC controlinformation, and when determination is made such that the referenceclock information is in the slot header, reception apparatus 20 extractsthe reference clock information from the slot header.

Also, the TMCC control information may store information indicating thatthe reference clock information is contained. FIG. 19 is a block diagramillustrating the functional configuration of reception apparatus 20 whenthe TMCC control information stores the information indicating that thereference clock information is contained within the slot header. FIG. 20is a diagram illustrating the acquisition flow of the reference clockinformation when the TMCC control information stores the informationindicating that the reference clock information is contained in the slotheader.

As illustrated in FIG. 19, in reception apparatus 20 when theinformation indicating that the reference clock information is containedwithin the slot header is stored in the TMCC control information,reference clock information extractor 15 acquires the reference clocksignal from the transfer slot that is output from decoder 11.

In the flow of FIG. 20, decoder 11 decodes the transfer channel codeddata (S131), analyzes the TMCC control information (S132), anddetermines whether the reference clock information is in the slot headerwithin the transfer slot (S133). When the reference clock information isin the slot header (Yes in S133), reference clock information extractor15 extracts the reference clock information from the slot header (S134),and reference clock generator 16 generates the reference clock of thesystem (system clock) based on the reference clock information (S135).On the other hand, when the reference clock information is not in theslot header (No in S133), the acquisition flow of the reference clockinformation ends.

Such reception apparatus 20, which can acquire the reference clockinformation in the layer of the transfer slot, can acquire the referenceclock information more quickly than a case where the reference clockinformation is stored in the TLV packet.

As described above, by storing the reference clock information in theTLV packet or transfer slot, reception apparatus 20 can reduce theprocesses until the acquisition of the reference clock information, andcan shorten acquisition time of the reference clock information.

In addition, by storing the reference clock information in a physicallayer in this way, acquisition and reproduction of the reference clockinformation by hardware can be implemented easily, and clockreproduction with high-precision is possible compared to the case ofacquisition and reproduction of the reference clock information bysoftware.

In addition, the aforementioned transmission method according to thefirst exemplary embodiment is summarized as, in the system in which theplurality of layers (protocols) exists including the IP layer, the timestamp of a medium is added based on the reference clock information inthe layers upper than the IP layer, and the reference clock informationis transmitted in the layers lower than the IP layer. Such aconfiguration facilitates processing of the reference clock informationby hardware in reception apparatus 20.

Based on a similar idea, the reference clock information may be storedin a condition of not being stored in the MMT packet within the IPpacket. Even in such a case, the processes for acquiring the referenceclock information can be reduced as compared with the case where thereference clock information is stored in the MMT packet.

[Transmission Cycle of the Reference Clock Information]

Hereinafter, a transmission cycle of the reference clock informationwill be supplemented.

In the case of storing the reference clock information in the TLVpacket, for example, time when the head bit of the TLV packet istransmitted on the transmission side is stored as the reference clockinformation. In addition, not the transmission time of the head bit butpredetermined time determined differently may be stored as the referenceclock information.

The TLV packet containing the reference clock information is transmittedat predetermined intervals. In other words, the TLV packet containingthe reference clock information is contained in the transfer slot and istransmitted in a predetermined transmission cycle. For example, at leastone or more pieces of reference clock information may be stored in theTLV packets and be transferred at intervals of 100 ms.

In addition, the TLV packets containing the reference clock informationmay be placed at predetermined intervals at predetermined positions ofthe transfer slot under the advanced BS transfer scheme. In addition,the TLV packet containing the reference clock information may be storedonce every 5-slot unit which is a slot assignment unit of the TLVpacket, and the reference clock information may be stored in the headTLV packet of the first slot of the 5-slot unit. That is, the TLV packetcontaining the reference clock information may be placed at a headwithin the head slot within the transfer slot (that is, immediatelyafter the slot header).

Also, the TLV packets that contain the reference clock information maybe placed at predetermined intervals at predetermined places of thetransfer slot under the transfer scheme for advanced broadband satellitedigital broadcast. For example, the reference clock information may bestored in the head TLV packet of the first slot once every 5-slot unitwhich is a slot assignment unit. That is, the reference clockinformation may be contained in the TLV packet positioned at a headwithin the head slot of each stream contained in the transfer slot.Also, the reference clock information may be stored in the first slotwithin the relative stream.

In addition, the transmission cycle and transmission interval of thereference clock information may be changed according to a modulationscheme or coding rate of the transfer channel coding scheme.

[Method for Acquiring the Reference Clock Information in the Upper LayerQuickly]

Next, a method will be described for shortening time to the acquisitionof the reference clock information by performing batch DEMUX processingfrom the lower layer to the upper layer in reception apparatus 20.

Here, a method will be described for storing the reference clockinformation in the upper layer such as the MMT packet, and for storingin the IP packet the MMT packet in which the reference clock informationis stored. In the method described below, direct reference of the MMTpacket which is the upper layer is made from the lower layer such as theTLV packet, by defining a protocol for storing in the TLV packet the IPpacket in which the reference clock information is stored. The referenceclock information contained in the MMT packet is acquired withoutperformance of normal DEMUX processing.

On the transmission side, the reference clock information is containedin the aforementioned control information stored in the MMT packet. Thepreviously determined packet ID is added to the control informationcontaining the reference clock information. Then, on the transmissionside, the MMT packet containing the reference clock information isstored in a dedicated IP data flow. The previously determined source IPaddress, destination IP address, source port number, destination portnumber, and protocol classification are added.

On receipt of the transfer channel coded data generated in this way,reception apparatus 20 can extract the IP packet containing thereference clock information by TLV demultiplexer 12 acquiring thepreviously determined IP data flow.

Note that when the IP packet undergoes header compression, for example,an identifier indicating that the IP packet contains the reference clockinformation is added to a context identifier indicating identical IPdata flows. The context identifier is stored in a compressed IP packetheader. In this case, reception apparatus 20 can extract the IP packetcontaining the reference clock information with reference to the contextidentifier in the compressed IP packet header.

In addition, the IP packet containing the reference clock informationmay be prescribed not to undergo the header compression, and may beprescribed to always undergo the header compression. It may beprescribed that the previously determined context identifier is added tothe IP packet containing the reference clock information, and that allthe headers are compressed.

In addition, such a method is also possible that a TLV data type fielddefines an identifier indicating that the TLV packet is an IP packetthat belongs to the IP data flow containing the reference clockinformation, or an identifier indicating that the TLV packet is acompressed IP packet that belongs to the IP data flow containing thereference clock information. Also, such an identifier may be defined ina field other than the TLV data type field.

When a direct reference to the reference clock information is made fromthe lower layer, the reference clock information is stored at apreviously determined position, and packets in which the reference clockinformation is stored (such as the MMT packet, IP packet, and TLVpacket) are packets dedicated to the reference clock information. Inaddition, a length of the field before the reference clock informationis fixed, such as a packet header length is fixed-length.

At this time, the length of the field before the reference clockinformation does not need to be fixed. The length of the field beforethe reference clock information only needs to be specified in the lowerlayer. For example, when information on the length to the referenceclock information includes two types, A and B, reception apparatus 20may specify the position of the reference clock information by signalingwhich of A and B the length information is in the lower layer.Alternatively, positional information on the reference clock informationthat allows direct reference to the reference clock information in theupper layer may be stored in the lower layer on the transmission side,and reception apparatus 20 may make a reference from the lower layerbased on the positional information.

The following describes a specific method for acquiring the referenceclock information in the upper layer quickly.

Reception apparatus 20 determines the TLV data type. On determinationthat the reference clock information is contained, reception apparatus20 acquires the reference clock information contained within the MMTpacket directly from the IP packet.

Thus, reception apparatus 20 may extract the reference clock informationcontained in the MMT packet by extracting a bit string at a specificposition from the IP packet or compressed IP packet, without analyzingthe IP address, port number, or context identifier. Extracting the bitstring at a specific position means, for example, extracting informationof a specific length from a position that is offset by fixed-lengthbytes from the TLV packet header. Accordingly, the reference clockinformation is acquired.

The offset length of the fixed-length bytes for extracting the referenceclock information is uniquely determined for each of the IP packet andthe compressed IP packet. Therefore, reception apparatus 20 can acquirethe reference clock information by extracting the information of thespecific length from the position that is offset by the fixed-lengthbytes immediately after determining the TLV data type. Note that theextraction here may be performed from a position that is offset by thefixed length from a specific field of TLV, instead of from the positionthat is offset by the fixed length from the TLV packet header.

Note that the aforementioned method is one example, and the referenceclock information in the upper layer may be acquired from the lowerlayer by defining another protocol or identifier. For example, anidentifier indicating whether the IP packet contains the reference clockinformation may be stored in a field other than the TLV data type field.

In addition, for example, reference time information contained in theMMT packet may be extracted by extracting the bit string of a specificposition from the IP packet or compressed IP packet without analyzingthe IP address, the port number, and the context identifier.

When the IP data flow containing the reference clock information is notdetermined from identification information on the IP data flow, the MMTpacket containing the reference clock information may be specified basedon unique identification information (packet ID) added to the MMT packetcontaining the reference clock information. In this case, the referenceclock information is extracted from the specific field as describedabove.

Also, it is assumed that the reference clock information contained inthe MMT packet is not stored at the position determined in advance orthat the position where the reference clock information contained in theMMT packet is stored cannot be specified. In such a case, receptionapparatus 20 specifies the MMT packet containing the reference clockinformation by using the aforementioned method, specifies the positionof the reference clock information based on MMT packet headerinformation, and extracts the reference clock information.

Note that, although an example has been described above in which the MMTpacket is stored in the IP packet, data to be stored in the IP packetdoes not need to be the MMT packet, but the data may be, for example,data that has another data structure. That is, the reference clockinformation may be contained in the IP packet in data structuredifferent from data structure of the MMT packet. Even for the data withdifferent data structure, in a similar manner to the aforementionedexample, data containing the reference clock information is stored in adedicated IP data flow, and identification information indicating thatthe data contains the reference clock information and identificationinformation indicating that the data is an IP data flow containing thereference clock information are added.

Reception apparatus 20 identifies that the data is data containing thereference clock information, and that the data is an IP data flowcontaining data containing the reference clock information. When thereference clock information is contained, reception apparatus 20extracts the reference clock information. Also, when the reference clockinformation is stored at a specific position of data, receptionapparatus 20 can extract the reference clock information contained inthe data with reference to the specific position from packet structureof the lower layer.

In the aforementioned example, in order to extract the reference clockinformation from the IP packet or the compressed IP packet, based onwhether the data is the IP packet or the compressed IP packet, receptionapparatus 20 extracts the reference clock information from respectivefixed-length offset positions different from each other. However, in acase where it is predetermined that the IP packet containing thereference clock information does not undergo header compression, or in acase where it is predetermined that all the IP packets containing thereference clock information undergo header compression, thedetermination on whether the data is the IP packet or compressed IPpacket made by reception apparatus 20 may be omitted. Also,determination on whether the reference clock information is containedmay be made after the header of the compressed IP packet isdecompressed.

A reception method for extracting a bit string of a specific positionfrom the IP packet or compressed IP packet will be described below withreference to the flowchart. FIG. 21 is a flowchart for extracting thebit string of a specific position from the IP packet or compressed IPpacket. Note that the configuration of reception apparatus 20 in thiscase is similar to the block diagram illustrated in FIG. 8.

In the flow of FIG. 21, first, decoder 11 decodes the transfer channelcoded data received by receiver 10 (S141), and extracts the TLV packetfrom the transfer channel slot (S142).

Next, TLV demultiplexer 12 analyzes the data type of TLV packet (S143),and determines whether the data type is an IP containing the referenceclock information (S144). When the determination is made such that thedata type is not an IP packet containing the reference clock information(No in S144), the flow ends. When the determination is made such thatthe data type is an IP packet containing the reference clock information(Yes in S144), the IP packet and the MMT packet are analyzed todetermine whether the IP header is compressed (S145).

When the IP header is not compressed (No in S145), reference clockinformation extractor 15 acquires the reference clock informationcontained within the MMT packet at a position that is offset byfixed-length N bytes from the TLV header (S146). When the IP header iscompressed (Yes in S145), reference clock information extractor 15acquires the reference clock information contained within the MMT packetat a position that is offset by fixed-length M bytes from the TLV header(S147).

For example, when it is determined in step S145 such that the IP headeris compressed, in step S146, reference clock information extractor 15acquires the reference clock information contained in the MMT packetfrom the position that is offset by N bytes from the TLV header. On theother hand, when it is determined in step S145 such that the IP headeris not compressed, in step S147, reference clock information extractor15 acquires the reference clock information contained in the MMT packetfrom the position that is offset by M bytes from the TLV header.

Finally, reference clock generator 16 generates the system clock basedon the reference clock information (S148).

Note that, since data structure of the IP packet header differsaccording to whether the IP packet is IPv4 or IPv6, the fixed-length Nbytes and M bytes have different values.

While the normal MMT packet containing audio, video, control signal, andthe like undergoes DEMUX processing in normal steps, the MMT packetcontaining the reference clock information undergoes batch DEMUXprocessing from the lower layer to the upper layer. This allowsacquisition of the reference clock information in the lower layer evenwhen the reference clock information is stored in the upper layer. Thatis, this can reduce the processes for acquisition of the reference clockinformation, shorten time to the acquisition of the reference clockinformation, and facilitate hardware implementation.

Second Exemplary Embodiment

Currently, as a method for using an extension area in TMCC controlinformation (hereinafter also simply referred to as TMCC) under anadvanced BS transfer scheme, ARIB (Association of Radio Industries andBusinesses) is studying a method for transmitting urgent information andthe like as a payload.

However, a proposed conventional method for using the extension area inthe TMCC control information is limited to a method for transmitting adata payload, such as text and images, by using the TMCC controlinformation extending over several frames. Therefore, the method forusing the extension area in the TMCC control information will belimited, in some cases.

In particular, control information (control signal) that does not changein value for each frame, such as a conventional transfer mode and slotinformation, or control information that changes in value for each framesuch as reference clock information cannot be stored in the extensionarea of the TMCC control information simultaneously with payload dataextending over several frames.

Therefore, the second exemplary embodiment describes a method for makingit possible to store data with different reception processingsimultaneously in the extension area of the TMCC control information, bydividing the extension area of the TMCC control information inaccordance with a classification of information and data to be stored inthe extension area of the TMCC control information. Providingextensibility to the use of the extension area by such a method canenhance flexibility of extension. Also, the reception apparatus canperform reception and analysis of the TMCC control information byreception methods different for each classification based on theclassification of data.

In addition, such a method allows payload data extending over severalframes and payload data of only one frame to be included together in theextension area. Since the payload data of only one frame can be acquiredfirst even while the payload data extending over several frames cannotbe received, urgent information can be acquired and presented morequickly.

[Structure of TMCC Extension Information]

Structure of TMCC extension information will be described below. Notethat basic structure of the TMCC control information is structureillustrated in FIG. 16. The control information to be stored in the TMCCcontrol information is classified roughly into a first type and a secondtype below.

The first type of control information relates to frames, and does notchange in value for each frame. A minimum update interval of suchcontrol information is a frame unit. When the value is changed,information after the change is transmitted two frames ahead. Also, whenthere is a change, notification is made by increment of an 8-bit changeinstruction. Specifically, information other than pointer informationand slot information corresponds to such control information.

The second type of control information relates to frames, and changes invalue for each frame. Since such control information is information thatchanges in value for each frame, the change instruction is not made.Specifically, such control information is the pointer information andthe slot information.

FIGS. 22A and 22B are diagrams respectively illustrating an example ofthe structure of the TMCC extension information, and an example of aconventionally proposed bit assignment method when the extension area isused as a payload. The TMCC extension information includes 16-bitextension identification and 3598-bit extension area as illustrated inFIG. 22A. Setting a value other than all 0 in the extensionidentification validates the extension area.

FIG. 22B is a diagram illustrating the example of the conventionallyproposed bit assignment method when the extension area is used as apayload. When the extension area is used as a payload, a number of pagesincludes 16 bits, and indicates over how many frames of the TMCC controlinformation during transfer an additional information payload istransferred.

A page number includes 16 bits, and indicates in which page the TMCCcontrol information during transfer is among the number of pages. Anadditional information classification includes 8 bits, and specifies theclassification of the additional information. Specifically, theadditional information classification is, for example, superimposedcharacters (subtitles), graphics, audio, and the like.

In a case of such structure, all of the extension area will be used as apayload, and control information such as the conventional TMCC controlinformation cannot be stored in the extension area by using theextension area.

[Extension Method of the TMCC Extension Area]

Here, a method will be described for implementing storage of data withdifferent reception processing in the TMCC extension area, by dividingthe TMCC extension area in accordance with the classification ofinformation and data to be stored in the TMCC extension area.

The classification of information or data to be stored in the TMCCextension area (hereinafter referred to as an extension classification)is classified as follows, for example.

Type A:

-   -   Type A indicates control information that relates to frames and        does not change in value for each frame.    -   Minimum update interval is a frame unit. When there is a change        in the value, information after the change is transmitted two        frames ahead.    -   Also, when there is a change, notification of the change is made        by increment of the 8-bit change instruction.

Type B:

-   -   Type B indicates control information that relates to frames and        changes in value for each frame.    -   Type B indicates information that changes in value for each        frame, and the change instruction is not made.

Type C:

-   -   Type C indicates information or data that is used as a payload        (conventional extension scheme).    -   However, for the change instruction, a change instruction field        which is identical to TMCC which is not the extension area may        be used, and the change instruction field may be independently        prescribed in the extension area.

FIG. 23 is a diagram illustrating an example of data structure (bitarrangement) of the extension area where the extension classificationclassified in this way is used. FIGS. 24A and 24B are diagramsrespectively illustrating first and second examples of the syntax whenthe extension classification is used.

In the example of FIG. 23, only the aforementioned three types aredefined as the extension classification. In addition, as illustrated inthe first example shown in FIG. 24A, subsequently to storage of a datalength in each of the three types of extension classification, extensiondata with a length indicated in the data length is stored for eachextension classification. The reception apparatus extracts data with thelength indicated in the data length from the extension area for eachextension classification, and performs processing.

For example, regarding data of Type A, the reception apparatus acquiresthe data only when there is a change instruction. When there is a changein the data of Type A, the reception apparatus considers that thecontrol information is changed, and performs processing on the controlinformation in accordance with the change.

Also, regarding data of Type B, since the data of Type B changes invalue for each frame, the reception apparatus acquires the data forevery frame. For example, when the reference clock information thatchanges in value for each frame is stored in the TMCC controlinformation, the reference clock information is stored in a data area ofType B.

Data of Type C contains payload information of the conventionalextension scheme. Regarding the data of Type C, the reception apparatusperforms operation in accordance with acquisition under the conventionalextension scheme.

In the aforementioned example, details of data structure for eachextension classification need to be separately prescribed. Whenprescribed separately, an identifier similar to the additionalinformation classification and an object service specification method inthe data of Type C illustrated in FIG. 22B may be prescribed in othertypes. Note that the additional information classification may bedefined using a common table, and the extension identification and theadditional information classification may be merged.

In addition, information that may change in the data length on the waymay be considered as a classification similar to the data of Type A. Inthis case, when there is a change in the data length, a changeinstruction may be made by transmitting information after the change twoframes ahead. When there is a change instruction, the receptionapparatus confirms whether there is any change in the data length withreference to the data length of the extension classification.

Note that the data structure is not limited to the structure asillustrated in FIG. 23. For example, when the data length of theextension classification is fixed in advance, the data length does notneed to be transmitted. Specifically, when the data length with theextension classification of Type A is fixed-length in FIG. 23, the datalength with the extension classification of Type A does not need to bedisposed within the data structure. In addition, when the data lengthwith the extension classification of Type A and the data length with theextension classification of Type B are fixed-length, the data length ofall types does not need to be disposed. In addition, a flag thatindicates whether there is any data of the extension classification maybe provided within the data structure.

In addition, syntax for using the extension classification is notlimited to the syntax of the first example illustrated in FIG. 24A. Forexample, in the second example illustrated in FIG. 24B, an extensionarea number is set, and the extension classification and extension arealength are stored for each extension area number. Subsequently, theextension data of the extension area number is stored.

Such structure may support addition of the extension classification inthe future. In addition, since such structure enables storage of aplurality of pieces of data with identical extension classification, itis not necessary to determine details of data structure for eachidentical extension classification in advance. In addition, even whenused as a payload (as Type C), such structure allows description of aplurality of pieces of data with different number of pages, such asvideo and audio in an identical frame.

Note that, in the structure of the second example illustrated in FIG.24B, the extension area number, extension classification, and extensionarea length may be classifications similar to Type A. That is, thesepieces of information may be prescribed to be information that followsthe change instruction. Thus, continuous storage of data that followsthe change instruction facilitates determination on presence of changes.

In addition, an undefined area may be provided in the extensionclassification in preparation for future extension. As an extensionclassification to be introduced in the future, for example, thefollowing classifications are assumed.

-   -   This is a control signal to be updated for each several frames,        and the change instruction is not made.    -   For an urgent signal, the change instruction is made in a        similar manner to Type A. However, processing of value change is        performed in the frame immediately after acquisition of the        change instruction, instead of after acquisition of information        that is two frames ahead.

Also, for the aforementioned urgent signal, an urgent flag may betransmitted using the extension classification accompanied by the changeinstruction, and urgent data may be transmitted using a payload. Also,the extension classification may be classified in accordance withwhether to follow the change instruction.

[Detailed Configuration and Operation Flow]

A functional configuration and operation flow of the reception apparatusas described above will be described. FIG. 25 is a block diagramillustrating the functional configuration of the reception apparatusaccording to the second exemplary embodiment. FIG. 26 is a diagramillustrating the operation flow of the reception apparatus according tothe second exemplary embodiment. Note that, in the followingdescription, the extension classification includes only three types,Type A, Type B, and Type C, as described above.

As illustrated in FIG. 25, reception apparatus 40 includes extensionidentifier 41, extension classification determiner 42, changeinstruction checker 43, data update checker 44, and update data acquirer45.

First, extension identifier 41 analyzes the extension identification ofthe TMCC control information (S161). When the extension identificationis other than all 0 here, extension identifier 41 determines that theextension area is effective, and reception apparatus 40 executes thefollowing processing for each extension area. Next, extensionclassification determiner 42 discriminates (determines) the extensionclassification (S162). When it is discriminated that the extensionclassification is Type A (Type A in S162), data of an area specified bythe extension area length is control information which does not changein value for each frame, the control information following a changeinstruction. Therefore, change instruction checker 43 checks the changeinstruction for each frame (S163).

Subsequently, data update checker 44 determines data update (S164). Whenit is determined that there is a change instruction and that there is achange in the extension data (Yes in S164), update data acquirer 45acquires updated extension data and executes processing accompanying thechange (S165).

On the other hand, when it is not determined as described above in stepS164 (No in S164), update data acquirer 45 determines that there is nochange in the extension data.

Also, when it is discriminated in step S162 that the extensionclassification is Type B (Type B in S162), update data acquirer 45references data specified by the extension area length, acquires dataupdated for each frame, and executes processing accompanying the change(S167).

When it is discriminated in step S162 that the extension classificationis Type C (Type C in S162), update data acquirer 45 executes processingbased on the conventional reception method under the payload extensionscheme (S166).

Note that, when it is discriminated that the extension area number,extension classification, and extension area length are classificationssimilar to Type A that follows the change instruction as describedabove, update data acquirer 45 checks change instructions. When there isa change instruction, update data acquirer 45 checks whether informationis updated.

Note that reception apparatus 40 may determine reception processingbased on the extension classification, and may determine in whichprocessing block the data processing should be performed. Receptionapparatus 40 may determine, for example, to process the data of Type Aand the data of Type B by hardware, and to process the data of Type C bysoftware.

[Advantageous Effects, Etc.]

As described above, the second exemplary embodiment has described themethod for dividing the TMCC extension area under the advanced BStransfer scheme for each extension classification, and for storing theextension data in the TMCC extension area. In such a method, receptionapparatus 40 determines the extension data processing method based onthe extension classification.

This makes it possible to store a plurality of pieces of data withdifferent reception processing in the TMCC extension areasimultaneously. That is, this makes it possible to provide extensibilityto the method for using the TMCC extension area.

Specifically, for example, it becomes possible to store the payload andthe reference clock information in the extension area simultaneously.

Also, it becomes possible to cause the payload data extending overseveral frames and the payload data of only one frame to be includedtogether in the TMCC extension area. Therefore, even while receptionapparatus 40 cannot receive the payload data extending over severalframes, reception apparatus 40 can first acquire the payload data ofonly one frame. Therefore, reception apparatus 40 can acquire andpresent urgent information more quickly.

Third Exemplary Embodiment

A third exemplary embodiment describes a method for transmitting aplurality of pieces of reference clock information that belong todifferent layers.

[Summary]

FIG. 27 is a diagram schematically illustrating an example in which thepieces of reference clock information are stored in the respectiveplurality of layers.

In the example of FIG. 27, a first layer is a layer upper than a secondlayer, and the first layer stores first reference clock information. Thesecond layer stores second reference clock information.

A transmission apparatus basically performs MUX processing in the secondlayer after performing MUX processing in the first layer. Also, areception apparatus basically performs DEMUX processing in the firstlayer after performing DEMUX processing in the second layer.

When storing the first reference clock information in the first layerand storing the second reference clock information in the second layer,as information that indicates a relationship between the first referenceclock information and the second reference clock information, thetransmission apparatus may store, for example, the followinginformation.

As a first example, the transmission apparatus allows a transmissionsignal (for example, a transfer frame) to include information indicatingthat the plurality of pieces of reference clock information is storedwithin the transmission signal.

Specifically, in at least one or more layers among the layers in whichthe reference clock information is contained, the transmission apparatusstores information indicating that the reference clock information isstored also in layers other than the aforementioned layers.

In addition, in a layer in which the reference clock information is notcontained, the transmission apparatus may indicate that the plurality ofpieces of reference clock information is stored. For example, thetransmission apparatus may store, in the lower layer (second layer),information that indicates whether the reference clock information iscontained in the upper layer (first layer). In this case, the receptionapparatus may determine whether to perform acquisition of the referenceclock information and reproduction of a reference clock in the lowerlayer in processing in the lower layer taking into consideration whetherthe reference clock information is contained in the upper layer.

As a second example, the transmission apparatus allows the transmissionsignal to include information regarding the first reference clockinformation and the second reference clock information.

Specifically, the transmission apparatus stores, in each layer,information that indicates a type of the reference clock informationcontained in the layer concerned. Alternatively, the transmissionapparatus stores, in each layer, information that indicates a type ofreference clock information contained in a layer other than the layerconcerned.

The reference clock information includes, for example, types such as32-bit NTP, 64-bit NTP, and 24-bit SMPTE (Society of Motion Picture andTelevision Engineers) time code. The information that indicates the typeof reference clock information is information that can specify a format(including information such as precision) of the reference clockinformation.

Note that, when it is known in advance that a predetermined type ofreference clock information is contained, such information does not needto be included.

As a third example, the transmission apparatus allows the transmissionsignal to include information that indicates a relative relationshipbetween the first reference clock information and the second clockinformation.

Specifically, the transmission apparatus allows the transmission signalto include information that indicates a relative relationship ofprecision of the reference clock information. For example, thetransmission apparatus allows the transmission signal to includeinformation that indicates whether precision of the second referenceclock information is high or low with respect to precision of the firstreference clock information.

In addition, such information that indicates the relative relationshipmay be information that indicates the relative relationship based onsize of a total bit number of the reference clock information, and maybe information that indicates the relative relationship of a dynamicrange based on size of a bit number of an integer part.

Alternatively, the information that indicates the relative relationshipmay be information that indicates the relative relationship of precisionof resolving power (resolution) based on size of a bit number of adecimal part. In addition, the information that indicates the relativerelationship may be information that indicates the relative relationshipof precision at a time of acquisition of the reference clockinformation, based on a difference in precision resulting from adifference in basic reliability of the reference clock information inthe transmission apparatus, quality of a transfer channel, andthroughput in transmission processing and reception processing.

In addition, the information that indicates the relative relationshipmay be information that indicates a difference in precision between eachof the pieces of reference clock information. For example, when there isa difference in the decimal bit number, the information that indicatesthe relative relationship may be information that indicates thedifference in the decimal bit number. The information that indicates therelative relationship may be information that indicates information thatindicates whether the precision differs for each, and may be stored asthe information that indicates the relative relationship only when theprecision differs for each. Note that, when the relative relationship ofprecision is known in advance, such information that indicates therelative relationship of precision does not need to be included.

In a case where such information that indicates the relativerelationship of precision is transmitted, when the transmittedinformation indicates that precision of the second reference clockinformation is low with respect to precision of the first referenceclock information, the reception apparatus can perform control includingavoiding performing acquisition and reproduction of the second referenceclock information, performing acquisition and reproduction of the firstreference clock information, and performing synchronous reproductionbased on the first reference clock information. Alternatively, when thetransmitted information indicates that precision of the second referenceclock information is high with respect to precision of the firstreference clock information, the reception apparatus can perform controlincluding avoiding performing acquisition and reproduction of the firstreference clock information, performing acquisition and reproduction ofthe second reference clock information, and performing synchronousreproduction based on the second reference clock information.

As a fourth example, the transmission apparatus allows the transmissionsignal to include information that indicates a relative relationship oftime between the pieces of reference clock information. Specifically,the transmission apparatus transmits information that indicates relativetime between the first reference clock information and the secondreference clock information. For example, the transmission apparatustransmits the information that indicates relative time by usingCRI_descriptor in an MMT scheme. Note that information may be includedindicating whether the first reference clock information and the secondreference clock information are generated based on an identicalreference clock.

When each of the pieces of reference clock information is generatedbased on an identical reference clock, in the reception apparatus, thereis usually a difference in acquisition timing between the firstreference clock information and the second reference clock information.That is, a fixed time difference arises between each of End-to-Enddelays of respective pieces of the reference clock information.

Therefore, the transmission apparatus calculates a time difference Δ_Abetween imparting timing of the first reference clock information andimparting timing of the second reference clock information, and storesthe calculated time difference Δ_A in the transmission signal as timecorresponding to acquisition timing of the first reference clockinformation and the second reference clock information. The receptionapparatus acquires the time difference Δ_A from the transmission signal,and corrects the End-to-End delay difference between the first referenceclock information and the second reference clock information based onthe time difference Δ_A.

In addition, when each piece of the reference clock information isgenerated based on the reference clock of an identical format and wheneach piece of the reference clock information has a fixed delaydifference Δ_B, the transmission apparatus stores and transmitsinformation that indicates the fixed delay difference Δ_B of thereference clock information. The reception apparatus acquires the delaydifference Δ_B, and corrects the fixed delay difference of the referenceclock based on the delay difference Δ_B.

In addition, when the reference clock on which each piece of thereference clock information is based has the fixed delay Δ_B, thetransmission apparatus transmits a transmission signal that includes thefixed delay Δ_B in the second layer, which is a lower layer.

In addition, when each piece of the reference clock information isgenerated based on the reference clock of an identical format, thesecond reference clock information may be represented with a differencefrom the first clock information based on the first reference clockinformation. In this case. The second reference clock information may beused as a base.

As a fifth example, when the plurality of pieces of reference clockinformation is stored, the transmission apparatus allows thetransmission signal to include information on whether to use thereference clock information stored in a different layer. Thetransmission apparatus allows the transmission signal to include, forexample, information as to instructions to use, in the first layer, thesecond reference clock information stored in the second layer. In thiscase, based on this information, the reception apparatus can decide togenerate the second reference clock information and to output thegenerated second reference clock information in the first layer.

The information described above is stored in at least one or morelayers. For example, regarding such information, the above-describedinformation may be stored only in the first layer, and may be storedonly in the second layer. Also, such information may be stored in bothof the layers. Alternatively, in each layer, information regarding thereference clock information in the layer may be stored, and onlyinformation that indicates the relative relationship may be stored in atleast one or more layers.

Note that the information that indicates the relative relationship ispreferably stored in the lower layer (second layer). Alternatively, theinformation that indicates the relative relationship may be stored in alayer lower than the second layer (not illustrated in FIG. 27). Thereception apparatus, which can acquire information regarding thereference clock information in the upper layer (first layer) whenperforming DEMUX processing in the lower layer (second layer), canperform higher-speed processing.

Note that a combination of the first layer and the second layer may beany combination. For example, the combination of the first layer and thesecond layer may be a combination of an MMT layer and an IP layer, acombination of an MMT layer and a transfer layer, and a combination ofan IP layer and a transfer layer. In addition, for MMToverTS, thecombination of the first layer and the second layer may be a combinationof MMT and TS.

In addition, the aforementioned information is stored in a controlsignal of each layer. For example, under the MMT scheme, theaforementioned information is stored in a descriptor, table, message, orpacket header information. Under an MPEG2-TS (Transport Stream) scheme,the aforementioned information is stored in a descriptor, table,section, or header information. In addition, the aforementionedinformation may be stored in TMCC or a slot header in the transferlayer. When a transfer scheme is DVB (Digital Video Broadcasting), theaforementioned information is stored in TPS (Transmission ParametersSignaling), L1 data, L2 data, P1 data, P2 data, and the like.

Note that the first reference clock information and the second referenceclock information may be pieces of reference clock information of anidentical type, and may be pieces of reference clock information ofdifferent types. Also, the first reference clock information and thesecond reference clock information may be pieces of reference clockinformation with different precision. The first reference clockinformation and the second reference clock information may be pieces ofreference clock information based on an identical reference clock, andmay be pieces of reference clock information based on differentreference clocks.

In addition, the transmission apparatus may transmit three or morepieces of reference clock information, and may store the three or morepieces of reference clock information in three or more respective layersfor transmission. In addition, the respective pieces of reference clockinformation may be stored in different fields within data structure inan identical layer. Another layer may exist between the first layer andthe second layer.

The reference clock information, which is, for example, NTP, time code,and PTP (Precision Time Protocol), may be reference clock informationother than these examples. In addition, the reference clock informationmay be another piece of information regarding time (for example, TOT(Time Offset Table) and TDT (Time Date Table)).

FIG. 28 is a diagram schematically illustrating an example in which aplurality of pieces of reference clock information is stored in onelayer. In the example of FIG. 28, in the first layer is contained threepieces of reference clock information, that is, first reference clockinformation, second reference clock information, and third referenceclock information.

Also in this case, the transmission apparatus may store informationregarding the first reference clock information and the second referenceclock information, information that indicates a relative relationship(of precision or time) between the first reference clock information andthe second reference clock information, and the like.

As one example, a case will be described of storing a plurality ofpieces of reference clock information in TMCC. As described in FIG. 17,16 streams can be transmitted under an advanced BS transfer scheme, andit is assumed that, for example, pieces of data of differentbroadcasting stations are stored in separate streams. FIG. 29 is a blockdiagram for describing an example in which the pieces of data ofdifferent broadcasting stations are stored in separate streams.

As illustrated in FIG. 29, each of first broadcasting station 51, secondbroadcasting station 52, and third broadcasting station 53 transmitsdata generated in each broadcasting station to satellite transmittingstation 54 by using cables, such as an optical network, and radio.Satellite transmitting station 54 multiplexes the streams of respectivebroadcasting stations into an identical transfer channel under theadvanced BS transfer scheme. Satellite transmitting station 54 stores inTMCC the pieces of reference clock information corresponding to therespective streams of the broadcasting stations, and transfers thepieces of reference clock information to reception apparatus 50.

In this case, in the example of FIG. 28, the first reference clockinformation corresponds to the reference clock information of firstbroadcasting station 51, the second reference clock informationcorresponds to the reference clock information of second broadcastingstation 52, and the third reference clock information corresponds tothird broadcasting station 53.

Meanwhile, in a case where each broadcasting station performs processingbased on common reference clock information, such as NTP, each piece ofreference clock information in satellite transmitting station 54 has atime difference due to a difference in the End-to-End delay caused by areception processing delay or a transfer delay until arrival at thesatellite transmitting station.

Here, when the common reference clock information to be used in eachbroadcasting station is NTP_base, the first reference clock informationin the satellite transmitting station is denoted as NTP_base+Δ1, thesecond reference clock information is denoted as NTP_base+Δ2, and thethird reference clock information is denoted as NTP_base+Δ3.

In this case, as illustrated in FIG. 30, the transmission apparatus maytransmit the common reference clock information NTP_base, and maytransmit pieces of difference information between the respective piecesof reference clock information and the common reference clockinformation (Δ1, Δ2, Δ3). FIG. 30 is a diagram for describing atransmission method of the pieces of difference information. Inaddition, for example, out of 64-bit reference clock information, basereference clock information is represented with top 16 bits, and thedifference information is represented with remaining 48 bits. Thisallows reduction in an amount of information (size) for transferring thereference clock information.

Note that the base reference clock information does not need to beNTP_base, but may be the earliest (with small delay) reference clockinformation among the plurality of pieces of reference clockinformation. Alternatively, the base reference clock information(reference value) may be a value smaller than a value of the earliestreference clock information.

Also, as illustrated in FIG. 31, the base reference clock informationand the difference information may be transmitted at differentfrequencies; for example, the base reference clock information istransmitted for every frame, and the difference information istransmitted in order for every three frames. FIG. 31 is a diagram fordescribing a variation of the transmission method of the differenceinformation. By the transmission method as illustrated in FIG. 31, theamount of information (size) for transferring the reference clockinformation can be reduced.

Reception apparatus 50 uses the base reference clock information toreproduce the base reference clock. After reproduction of the basereference clock information, reception apparatus 50 may use thedifference information to generate each reference clock.

[Detailed Configuration and Operation Flow]

Here, a functional configuration and operation flow of receptionapparatus 50 will be described. FIG. 32 is a block diagram illustratingthe functional configuration of reception apparatus 50. FIG. 33 is adiagram illustrating the operation flow of reception apparatus 50. Here,the following describes an example in which the reference clockinformation is stored in only either one of the IP layer and thetransfer layer, and based on the reference clock information stored ineither one of the IP layer and the transfer layer, reception apparatus50 reproduces the reference clock.

Reception apparatus 50 includes receiver 10, decoder 11, TLVdemultiplexer 12, IP demultiplexer 13, MMT demultiplexer 14,synchronizer 17, and decoding presenter 18. In addition, receptionapparatus 50 includes first reference clock information extractor 15 a,second reference clock information extractor 15 b, first reference clockgenerator 16 a, and second reference clock generator 16 b.

A flag that indicates whether the pieces of reference clock informationis in the IP layer is stored in control information of the transferlayer (such as slot header and TMCC, herein TMCC). In addition, whenthere is no reference clock information in the IP layer, the referenceclock information is stored in the control information of the transferlayer.

In addition, in the control information of the transfer layer is stored,when there is no reference clock information in the IP layer, a flagthat indicates whether the reference clock information acquired in thetransfer layer is necessary for processing in the upper layer, or a flagthat indicates whether the reproduced reference clock information isnecessary for processing in the upper layer.

For example, when the reference clock information is 64-bit NTP, NTP isstored in a 64-bit field that indicates reference clock information. Inaddition, a flag that indicates whether the reference clock informationis in the IP layer may be provided in the field for reference clockinformation. Since the reference clock information does not need to bestored in the transfer layer when the reference clock information isstored in the IP layer, the field may be utilized.

For example, in a case where a predetermined value (for example, ALL 1)is in the field for reference clock information when the reference clockinformation is in the IP layer, reception apparatus 50 determines thatthe value is not reference clock information but is the flag thatindicates that the reference clock information is in the IP layer.Alternatively, a value based on a predetermined rule may be used as aflag; for example, when ALL 1 is indicated only once in the field forreference clock information, reception apparatus 50 determines that thereference clock information is in the field, and when ALL 1 is indicatedcontinuously more often than a predetermined number of times, receptionapparatus 50 determines that the reference clock information is in theIP layer.

Decoder 11 of reception apparatus 50 analyzes TMCC, which is controlinformation, in the transfer layer, and analyzes various flags and thereference clock information (S171). Then, decoder 11 makes adetermination based on the aforementioned flags (S172). When it isdetermined that the reference clock information is not in the IP layer(the reference clock information is in the transfer layer) (No in S172),second reference clock information extractor 15 b acquires (extracts)the reference clock information in the transfer layer, and secondreference clock generator 16 b reproduces (generates) the referenceclock.

Next, decoder 11 makes a determination on whether the reference clockreproduced in the transfer layer is necessary for processing in theupper layer (S174). When it is determined that the reference clockreproduced in the transfer layer is necessary for processing in theupper layer (Yes in S174), second reference clock generator 16 b outputsthe reference clock reproduced in step S174 to the upper layer (S175).When it is not determined that the reference clock reproduced in thetransfer layer is necessary for processing in the upper layer (No inS174), the processing ends.

On the other hand, when it is determined that the reference clockinformation is in the IP layer (the reference clock information is notin the transfer layer) (Yes in S172), acquisition of the reference clockinformation and reproduction of the reference clock are not performed inthe transfer layer. In this case, acquisition of the reference clockinformation and reproduction of the reference clock are performed in theIP layer by first reference clock information extractor 15 a and firstreference clock generator 16 a, respectively (S176).

Note that, when reproduction of the reference clock is not necessary inthe transfer layer, and when the upper layer does not need the referenceclock, acquisition of the reference clock information and reproductionof the reference clock in the transfer layer (S173) do not need to beperformed.

In addition, when the reference clock is necessary in the upper layer,instead of outputting the reproduced reference clock, the referenceclock information may be passed to the upper layer, and reproduction ofthe reference clock may be performed in the upper layer. In addition,based on the reference clock reproduced in the transfer layer, referenceclock information may be newly generated, and the generated referenceclock information may be output to the upper layer.

Methods for outputting the reference clock to the upper layer include amethod for outputting the reproduced reference clock as it is, and amethod for storing or converting and outputting the acquired referenceclock information or newly generated reference clock information intodata structure to be output to the upper layer.

[Another Example of Operation Flow]

Next, another operation flow of reception apparatus 50 will bedescribed. FIG. 34 is a diagram illustrating another operation flow ofreception apparatus 50. Note that the configuration of receptionapparatus 50 is similar to the configuration of FIG. 32.

In the example of FIG. 34, the reference clock information may be storedin each of the IP layer and the transfer layer. When a plurality ofpieces of reference clock information is stored, relative information onprecision of the pieces of reference clock information is stored.

Decoder 11 analyzes TMCC (S181) and makes a determination based on theflags (S182). When it is determined that the reference clock informationis not in the IP layer (No in S182), acquisition of the reference clockinformation and reproduction of the reference clock are performed in thetransfer layer (S185).

On the other hand, when it is determined in step S182 that the referenceclock information is in the IP layer (Yes in S182), decoder 11determines which of the reference clock information in the transferlayer and the reference clock information in the IP layer has higherprecision (S183). When it is determined that the reference clockinformation in the IP layer has higher precision than the referenceclock information in the transfer layer (Yes in S183), acquisition ofthe reference clock information and reproduction of the reference clockare performed in the IP layer (S184). When it is determined that thereference clock information in the IP layer has lower precision than thereference clock information in the transfer layer (No in S183),acquisition of the reference clock information and reproduction of thereference clock are performed in the transfer layer (S185).

[Advantageous Effects, Etc.]

As described above, a plurality of pieces of reference clock informationmay be transmitted in one or more layers. When the plurality of piecesof reference clock information is transmitted, reception apparatus 50may select either one piece of the reference clock information to beused for generation of the reference clock (system clock), and may useboth pieces of the reference clock information to generate the referenceclock. At this time, reception apparatus 50 may select high-precisionreference clock information, and may select reference clock informationthat can be acquired more quickly.

In addition, when the reference clock information is transmitted in aplurality of layers, information indicating that the reference clockinformation is transmitted in the plurality of layers may be stored on atransmission side. In addition, information indicating that thereference clock information is transmitted in the plurality of layers,or information related to the layers or protocols in which the referenceclock information is transmitted may be transmitted in the lower layer.Furthermore, information that indicates a relationship between thepieces of reference clock information stored in different layers may betransmitted.

This allows reception apparatus 50 to determine that the reference clockinformation is contained in the upper layer during DEMUX processing inthe lower layer, and to decide which reference clock information to usebased on this determination. The decision on which reference clockinformation to use may be made based on which layer of reference clockreproduction reception apparatus 50 supports, and recommended referenceclock reproduction may be specified by broadcasting stations.

When the reference clock information is transmitted in the plurality oflayers, reception apparatus 50 may extract the reference clockinformation in the lower layer, and may extract, from the lower layer,the reference clock information contained in the upper layer. Then,reception apparatus 50 may use at least one or more pieces of extractedreference clock information to generate the reference clock.

Here, the plurality of pieces of reference clock information may betransmitted through a plurality of transfer channels. In this case,information indicating that the plurality of pieces of reference clockinformation is transmitted through the plurality of transfer channels,and information related to the transfer channels through which thereference clock information is transferred may be transmitted.

Other Exemplary Embodiments

While the exemplary embodiments have been described above, the presentdisclosure is not limited to the aforementioned exemplary embodiments.

For example, it is assumed that, in addition to the conventional 32-bitshort-format NTP contained in the MMT packet header, higher-precisionreference clock information is transmitted. In such a case, informationfor allowing the reception apparatus to use the high-precision referenceclock information to reproduce the 32-bit short-format NTP is furthertransmitted from the transmission side. Such information is, forexample, time information indicating a relative relationship betweeneach of clocks, and a configuration for transmitting the information byusing CRI_descriptor( ), etc. may be considered.

Note that, when the reception apparatus can reproduce the 32-bitshort-format NTP, the conventional NTP field contained in the MMT packetheader is unnecessary. Therefore, another piece of information may bestored in the NTP field, and header compression may be performed throughreduction of the NTP field. When header compression is performed,information indicating that the NTP field is reduced is transmitted.When the NTP field is reduced, the reception apparatus generates thereference clock by using another piece of reference clock information,and reproduces the 32-bit short-format NTP.

In addition, when the MMT packet is transferred using a broadbandtransfer channel, the reception apparatus may use not the referenceclock information but the 32-bit short-format NTP for QoS control.Accordingly, the reference clock information does not need to betransmitted through the broadband transfer channel. In addition, whenthe End-to-End delay of the broadband transfer channel is within acertain value, the reference clock information may be used for clockreproduction.

Note that although the aforementioned first exemplary embodiment hasdescribed the case where the MMT/IP/TLV scheme is used as an example,schemes other than the MMT scheme may be used as a multiplexing scheme.For example, the present disclosure may also be applied to an MPEG2-TSscheme, RTP scheme, or MPEG-DASH scheme.

In addition, methods for header compression of IP packets include RoHC(Robust Header Compression) and HCfB (Header Compression forBroadcasting).

Schemes for storing IP packets in broadcast include a GSE (GenericStream Encapsulation) scheme, IPoverTS scheme using ULE (UnidirectionalLight-weight. Encapsulation), and the like, in addition to the TLVscheme.

The present disclosure may be applied to a case where any of suchschemes is used. Application of the present disclosure allows thereception apparatus to achieve shortening of time to the acquisition ofthe reference clock information and reduction in the processes, and toachieve high precision of the clock by hardware implementation.

Note that, while the reference clock information in the aforementionedexemplary embodiments is NTP when the multiplexing scheme is MMT, forexample, when the multiplexing scheme is an MPEG2-TS scheme, thereference clock information is PCR (Program Clock Reference). Also, evenwhen the multiplexing scheme is MMT, PTP prescribed by IEEE (Instituteof Electrical and Electronics Engineers) 1588 may be transferred in anNTP form. Only some bits of NTP may be transferred. That is, thereference clock information only needs to be information indicating timethat is set on a transmission side. Note that NTP does not necessarilymean an NTP value in an NTP server commonly used on the Internet.

In addition, the present disclosure may be implemented as a transmissionapparatus (transmission method) that transmits the transfer slot thatstores the reference clock information by the aforementioned method. Aconfiguration of such a transmission apparatus will be supplementedbelow. FIG. 35 is a block diagram illustrating a functionalconfiguration of the transmission apparatus. FIG. 36 is an operationflow of the transmission apparatus.

As illustrated in FIG. 35, transmission apparatus 30 includes generator31 and transmitter 32. Note that each component of transmissionapparatus 30 is specifically implemented by a microcomputer, aprocessor, a dedicated circuit, or the like.

Transmission apparatus 30 is specifically a broadcasting server, and isan example of the aforementioned “transmission side” of the firstexemplary embodiment.

Generator 31 generates, for example, a transfer slot that stores aplurality of slots that each store one or more TLV packets that eachstore an IP packet (S151 of FIG. 36).

At this time, generator 31 allows the IP packet stored in the TLV packetpositioned at a head within the head slot within the transfer slot(hereinafter this IP packet is also referred to as an object IP packet)to contain the first reference clock information, such as NTP, thatindicates time for playback of content (for example, broadcast contentsuch as video and audio). At this time, the object IP packet is an IPpacket that does not undergo header compression, and the first referenceclock information is stored, for example, within the object IP packet indata structure different from data structure of the MMT packet.

In addition, generator 31 stores the second reference clock informationthat indicates time for playback of content in control information(TMCC) within the transfer slot.

Specifically, generator 31 includes a coder that codes the broadcastcontent, MMT multiplexer, IP multiplexer, TLV multiplexer, and the like.Here, the TLV packet is an example of a first transfer unit, the slot isan example of a second transfer unit, and the transfer slot is anexample of a transfer frame.

Transmitter 32 transmits the transfer slot generated by generator 31(transfer channel coded data containing the transfer slot) throughbroadcast (S152 of FIG. 36).

As also described in the aforementioned exemplary embodiments, suchtransmission apparatus 30 can simplify the processes by which thereception apparatus acquires the reference clock information. Therefore,this can shorten time until the reception apparatus acquires thereference clock information.

In addition, since the second reference clock information that indicatesthe time for playback of the content is stored in the controlinformation within the frame, the reception apparatus can select whichreference clock information to use from among the first reference clockinformation and the second reference clock information.

Fourth Exemplary Embodiment

The present exemplary embodiment describes a method for passingreference clock information to an upper layer and an interface thereofin a reception apparatus.

FIG. 37 is a block diagram illustrating a configuration of receptionapparatus 60 according to the present exemplary embodiment. Receptionapparatus 60 includes decoding apparatus 61 that performs processes in alower layer and demultiplexing apparatus 62 that performs processes inan upper layer. For example, decoding apparatus 61 and demultiplexingapparatus 62 are formed as different LSIs. Note that decoding apparatus61 and demultiplexing apparatus 62 may be formed as a single LSI.

Decoding apparatus 61 includes receiver 10 and decoder 11. Receiver 10receives transfer channel coded data. Decoder 11 extracts a TLV packetby decoding the transfer channel coded data received by receiver 10, andoutputs the TLV packet to demultiplexing apparatus 62.

Demultiplexing apparatus 62 includes acquirer 63 and demultiplexer 64.Acquirer 63 acquires the TLV packet that is output from decodingapparatus 61. Demultiplexer 64 demultiplexes the TLV packet. Forexample, demultiplexer 64 includes processors other than receiver 10 anddecoder 11 among processors illustrated in FIG. 32. Note thatdemultiplexer 64 may include processors other than receiver 10 anddecoder 11 among processors included in reception apparatuses describedin other exemplary embodiments. In addition, demultiplexer 64 does notneed to include all of these processors, and may include only some ofthese processors. In addition, demultiplexing apparatus 62 controlsoutput of decoding apparatus 61.

Capturing and detailed description are provided about a method by which,as described in FIG. 32 and FIG. 33, when the reference clockinformation is contained in the lower layer, decoding apparatus 61 ofthe lower layer passes the reference clock information to demultiplexingapparatus 62 without outputting a reproduced reference clock todemultiplexing apparatus 62 of the upper layer, and demultiplexingapparatus 62 reproduces the reference clock.

The following describes a method described in NPTL 2 (Chapter 3:“Guideline for Time Information Transmission” in ARIB Standard ARIBSTD-B44 (Ver. 2.0) “TRANSMISSION SYSTEM FOR ADVANCED WIDE BAND DIGITALSATELLITE BROADCASTING”), and transmission and reception of thereference clock based on data structure.

Although the aforementioned standard describes a method for storing thereference clock information in TMCC, this standard does not prescribespecific transmission time information and operations in the receptionapparatus, and does not allow the reception apparatus to acquireaccurate time information. For example, although this standard describesthat “the reference clock information to be stored in TMCC is time whenthis TMCC signal leaves a transmission server”, this is not a specificdefinition.

TMCC control information (TMCC control signal) is generated in aseparate system from a main signal of a main line system for eachtransfer frame in a transmission apparatus. After error correctioncoding and an interleave process are performed, the TMCC controlinformation is dispersively mapped in the main signal for one frame (themain signal is also a signal after the error correction coding andinterleave process are performed).

FIG. 38 is a diagram illustrating timing of the main signal and thereference clock information.

When the reference clock information is stored in the TMCC controlinformation, the reference clock information (NPTn, NPTn+1, . . . inFIG. 38) is generated at intervals of a transfer frame time length(T_(F)). After being generated, the reference clock information istransmitted in a transfer frame unit. At this time, during a period fromgeneration of the reference clock information to transmission of thetransfer frame, processing delay occurs caused by error correctioncoding, interleave process, transfer frame transmission timing, and thelike. In FIG. 38, NTPn is stored in transfer frame M+1 and transferred,whereas NTPn+1 is stored in transfer frame M+2 and transferred. Here,description is provided assuming that transfer delay is 0 andtransmission time and reception time of the transfer frame areidentical.

The reception apparatus receives data of one transfer frame, performsthe error correction process and deinterleave process, and then extractsthe TMCC control information. Accordingly, reception timing of thereference clock information is delayed by one or more frames.

Similarly, processing delay also occurs in transmission and reception ofthe main signal of the main line system due to error correction andinterleave process.

However, since delay time differs in each of transmission and receptionbetween the main line system and a TMCC control information system, itis unclear to which time of the main line system time the time of thereference clock information acquired by the reception apparatuscorresponds. In addition, timing is not prescribed at which to store inthe upper layer the reference clock information acquired by thereception apparatus.

Therefore, according to the present exemplary embodiment, the referenceclock information is stored in the TMCC control information by thefollowing method.

The transmission apparatus sets, for example, time when the transferframe of the main signal transmits a server (for example, time when ahead packet of the transfer frame transmits the server) as the referenceclock information to be stored in the TMCC control information.

The reception apparatus stores the reference clock information extractedfrom the TMCC control information at a head position of the nexttransfer frame, and then transfers the reference clock information tothe upper layer.

By the above-described operation, a relative relationship caused by adifference in processing delay between the main line system and the TMCCcontrol information system is an integral multiple of the transfer frame(N×T_(F)) (N is an integer).

Furthermore, correction of N× T_(F) is performed in order to match atime relationship between the main line system and the reference clockinformation extracted from the TMCC control information.

When N can be uniquely determined in advance, the transmission apparatusmay store the time on which the N×T_(F) correction is performed in theTMCC control information, and the reception apparatus may correct thetime. When N cannot be uniquely determined, the reception apparatusestimates N and corrects the time.

In addition, when the reference clock information is transferred in themain signal (TLV packet) in addition to the TMCC control information,the transmission apparatus stores, in the TMCC control information, timeidentical to time to be stored in the TLV packet. Alternatively, thetransmission apparatus stores in the TMCC control information the timeobtained by performing correction according to N×T_(F) on the time to bestored in the TLV packet.

By applying correction of N×T_(F) to time information extracted from theTMCC control information, the reception apparatus calculates the timeidentical to the time to be stored in the main signal, and outputs thecalculated time to the upper layer.

Note that as a method for extracting the reference clock informationfrom the TMCC control information and transferring the correctedreference clock information to the upper layer, the reception apparatusmay replace and output the reference clock information within the TLVpacket.

In addition, since time that serves as reference is identical between inthe reference clock information stored in the TMCC control informationand in the reference clock information stored in the TLV packet, it ispossible to handle these pieces of reference clock information asidentical information in the upper layer.

In addition, reception apparatus 60 may switch with a selecting switchor the like between a method for outputting only one of the referenceclock information stored in the TMCC control information and thereference clock information stored in the TLV packet as a main signal(TLV packet), and a method for outputting both pieces of theinformation. In addition, demultiplexing apparatus 62 in the upper layermay select this switching in the lower layer. In addition, when decodingapparatus 61 is physically different from demultiplexing apparatus 62,one of the methods may be selected with a register or the like. Inaddition, when only one of the reference clock information stored in theTMCC control information and the reference clock information stored inthe TLV packet is output, selection may be made which one to output.

Here, when the reference clock information is transferred in the mainsignal (TLV packet), the reference clock information is stored in a headTLV packet of a head slot of the TLV stream in the transfer frame.Therefore, decoding apparatus 61 can uniquely identify the TLV packet inwhich the reference clock information is stored in the transfer layer.

However, demultiplexing apparatus 62 of the upper layer, which cannotknow boundary information of the transfer frame, can determine whetherthe received TLV packet contains the reference clock information afteranalysis of the TLV packet header and the IP packet header. Therefore,according to the present exemplary embodiment, decoding apparatus 61 ofthe lower layer performs signaling (notification) to demultiplexingapparatus 62 of the upper layer such that the TLV packet is a head ofthe TLV stream in the transfer frame, or that the TLV packet containsthe reference clock information. Accordingly, demultiplexing apparatus62 of the upper layer can detect that the TLV packet contains thereference clock information without analyzing the IP packet header.

Examples of the method for performing signaling that the TLV packet is ahead of the TLV stream in the transfer frame or that the TLV packetcontains the reference clock information include a method for utilizingan undefined region in a packet type of the TLV packet.

For example, when the reference clock information is contained in anIPv4 packet, decoding apparatus 61 rewrites the TLV type from the TLVtype that indicates the IPv4 packet to the TLV type that indicates theIPv4 packet containing the reference clock information. Then, decodingapparatus 61 outputs the rewritten TLV packet to demultiplexingapparatus 62. In addition, when the reference clock information iscontained in an IPv6 packet, decoding apparatus 61 rewrites the TLV typefrom the TLV type that indicates the IPv6 packet to the TLV type thatindicates the IPv6 packet containing the reference clock information.Then, decoding apparatus 61 outputs the rewritten TLV packet todemultiplexing apparatus 62.

In addition, reception apparatus 60 may have a switch or the like thatallows selection whether decoding apparatus 61 performs signaling todemultiplexing apparatus 62 that the TLV packet contains the referenceclock information. For example, this selection may be performed bydemultiplexing apparatus 62.

The above processes enable acquisition of high-precision reference clockinformation and clock reproduction.

FIG. 39 is a diagram illustrating an operation flow in decoder 11 ofreception apparatus 60.

First, decoder 11 decodes the transfer frame (S191), and subsequentlydetermines whether the reference clock information to be processed isthe reference clock information stored in TMCC or the reference clockinformation stored in the main signal (S192). When processing thereference clock information stored in the main signal (main signal inS192), decoder 11 outputs the TLV packet as it is to the upper layer(S193). Meanwhile, when processing the reference clock informationstored in the TMCC control information (TMCC in S192), decoder 11extracts the reference clock information from the TMCC controlinformation, corrects the extracted reference clock information, storesthe corrected reference clock information in the head TLV packet of theTLV stream in the transfer frame, and outputs the TLV packet todemultiplexing apparatus 62 (S194).

FIG. 40 is a diagram illustrating an operation flow in receptionapparatus 60 including decoder 11.

First, demultiplexing apparatus 62 (upper layer) designates thereference clock information to be output to demultiplexing apparatus 62from decoding apparatus 61 (S201). When the reference clock informationto be output to demultiplexing apparatus 62 is the reference clockinformation contained in the main signal (main signal in S202), decodingapparatus 61 outputs the TLV packet as it is to demultiplexing apparatus62 (S203). Meanwhile, when the reference clock information to be outputto demultiplexing apparatus 62 is the reference clock information storedin the TMCC control information (TMCC in S202), decoding apparatus 61extracts the reference clock information from the TMCC controlinformation, corrects the extracted reference clock information, storesthe corrected reference clock information in the head TLV packet of theTLV stream in the transfer frame, and outputs the TLV packet todemultiplexing apparatus 62 (S204).

FIG. 41 is a diagram illustrating an operation flow in demultiplexingapparatus 62 when decoding apparatus 61 performs signaling in the TLVpacket type about whether the TLV packet contains the reference clockinformation.

First, demultiplexing apparatus 62 analyzes the packet type of TLVpacket acquired from decoding apparatus 61 (S211) to determine whetherthe TLV packet contains the reference clock information (S212).

When the TLV packet contains the reference clock information (Yes inS212), demultiplexing apparatus 62 acquires the reference clockinformation without analyzing the IP packet header (S213). This enablesreduction in processing time and reduction in the amount of processes.

Meanwhile, when the TLV packet does not contain the reference clockinformation (No in S212), demultiplexing apparatus 62 performs normalTLVDemux and IPDemux because the TLV packet does not contain thereference clock information (S214).

Note that when an IP data flow of broadcasting services has two typesincluding an IP data flow that stores the MMT packet and an IP data flowthat stores the reference clock information, reception apparatus 60identifies the reference clock information in accordance with the TLVpacket type, eliminating the need for analysis of the IP address. Thisis because, by identifying the reference clock information in accordancewith the TLV packet type, there is one IP data flow that stores thereference clock information and one IP data flow that stores the MMTpacket, eliminating the need for analysis of the IP address foridentifying the IP data flow that stores the MMT packet.

As described above, decoding apparatus 61 and demultiplexing apparatus62 according to the present exemplary embodiment perform the followingprocesses.

FIG. 42 is a diagram illustrating an operation flow in decodingapparatus 61 according to the present exemplary embodiment.

First, receiver 10 receives the transfer slot (S221). The transfer slotis a transfer frame that stores a plurality of slots (second transferunits) that each contain one or more TLV packets (first transfer units)obtained by multiplexing the content, as illustrated in FIG. 13. Inaddition, as described above, the TLV packet positioned at a head withinthe head slot within the transfer slot contains the reference clockinformation.

Next, decoder 11 acquires a plurality of TLV packets by decoding thetransfer slot. In addition, decoder 11 further generates information foridentifying the TLV packet positioned at a head within the head slotwithin the transfer slot (S222).

Specifically, decoder 11 stores information indicating that the TLVpacket contains the reference clock information as managementinformation (packet type) of the TLV packet stored in the TLV packetpositioned at a head within the head slot within the transfer slot.Alternatively, the information for identifying the TLV packet positionedat a head within the head slot within the transfer slot is informationthat indicates the TLV packet positioned at a head within the head slotwithin the transfer slot among the plurality of TLV packets within thetransfer slot.

That is, decoder 11 generates the information for identifying the TLVpacket positioned at a head within the head slot within the transferslot, and notifies the information to demultiplexing apparatus 62.Specifically, decoder 11 adds the information within the TLV packet, ornotifies the information to demultiplexing apparatus 62 by anothersignal.

Next, decoder 11 outputs the TLV packet containing the information, orthe TLV packet and the information to demultiplexing apparatus (S223).

FIG. 43 is a diagram illustrating an operation flow in demultiplexingapparatus 62 according to the present exemplary embodiment.

First, acquirer 63 acquires the transfer slot from decoding apparatus 61(S231). Here, when each of the TLV packets contains the reference clockinformation, the TLV packet contains the management information (packettype) indicating that the TLV packet contains the reference clockinformation.

Demultiplexer 64 identifies the TLV packet containing the referenceclock information based on the management information (S232), andacquires the reference clock information from the identified TLV packet(S233). In addition, demultiplexer 64 acquires the content bydemultiplexing the plurality of TLV packets (S234).

As described above, in reception apparatus 60 according to the presentexemplary embodiment, the information for identifying the TLV packetcontaining the reference clock information is notified from decodingapparatus 61 to demultiplexing apparatus 62. This allows demultiplexingapparatus 62 to acquire the reference clock information withoutanalyzing the IP packet header and the like, achieving reduction in theamount of processes and high speed.

Fifth Exemplary Embodiment

The present exemplary embodiment provides a supplementary description ofthe method, which has been described with reference to FIG. 11 to FIG.17, for storing a TLV packet that contains reference clock informationinto a head TLV in the first slot of each relative stream of a transferframe (transfer slot). Here, one transfer frame includes one or pluralrelative streams.

The pointer/slot information in the TMCC control signal shown in FIG. 16indicates a head location of the first packet and an end location of thelast packet, included in each slot. A top pointer value indicates thelocation of the first byte of the first packet in the slot by the numberof bytes counted from a slot header excluding the slot header. Note that“0xFFFF” indicates that the first byte is absent. A last pointer valueindicates the value obtained by adding 1 to the number of bytes countedfrom a slot header excluding the slot header up to the final byte of thelast packet, in the slot, of which the placement has been completed.Note that “0xFFFF” indicates that the final byte is absent.

For example, in the example of Slot #120 shown in FIG. 45, the toppointer indicates the first byte location of TLV #(n−2) whereas the lastpointer indicates the value (first byte location of TLV #(n−1)) obtainedby adding 1 to the final byte location of TLV #(n−2).

In the case where a TLV packet containing reference clock information isstored in the head of the first slot for each relative stream, the toppointer value in the slot/pointer information of the slot indicates 0.Naturally, a TLV packet is not stored across the frames, and shall bestored so that the location of the final byte of the last TLV packetstored in the last slot of each relative stream (hereinafter referred toas “final TLV packet”) corresponds to the location of the final byte ofthe last slot of each relative stream (hereinafter referred to as “frameboundary of each relative stream”).

FIG. 44 shows a structure of the transfer frame that does not includereference clock information, and FIG. 45 shows a structure of thetransfer frame that includes reference clock information in the head ofthe first slot.

Here, the case where one frame is made up of 120 slots and all of the120 slots make one relative stream is shown as an example. Slot #120 isthe last slot of the relative stream of the transfer frame M, Slot #1 isthe first slot of the relative stream of the transfer frame M+1, and thefinal byte of Slot #120 of the transfer frame M and the first byte,excluding the slot header, of Slot #1 of the transfer frame M+1 are theframe boundary of the TLV stream.

In FIG. 44, TLV #n is placed across the frames. In contrast, in FIG. 45,the TLV packet is not placed across the frames because the referenceclock information is placed in the first slot (Slot #1) of the relativestream. In other words, the final byte of Slot #120 of the transferframe M shall be placed so that its location corresponds to the locationof the final byte of TLV #(n−1).

Here, transfer control information, an IP packet, or a compressed IPpacket is stored in a TLV packet which has a variable-length packetsize. When the variable-length TLV packets are sequentially placed intofixed-length transfer frames, the end of the final TLV packet does notcoincide with a frame boundary in some cases. In such case, by placing aTLV packet having a data type that is NULL, the final byte of the finalTLV packet can be adjusted to coincide with the frame boundary. Here,the NULL packet having the data type NULL is a packet for storing thedata which is invalid and is not used in the reception apparatus.

As shown in FIG. 46, the TLV packets are placed into the frames for eachrelative stream. After the TLV packet TLV #(n−1) has been placed into aframe, a NULL packet is placed instead of the packet TLV #n because thepacket TLV #n cannot be placed into the same frame. Accordingly, thefinal byte of the NULL packet coincides with the frame boundary.

However, in some cases, due to the data structure of the TLV packet, therestrictions on the transmission apparatus or the reception apparatus,and the like, minimum and maximum values might be provided for the sizeof the TLV packet. For example, because the header of the TLV packet is4 bytes, even when NULL of 0 bytes is placed in the payload of the TLVpacket, the TLV packet size is 4 bytes. Therefore, the minimum value ofthe TLV packet size in this case is 4 bytes. Moreover, due to therestrictions on the transmission apparatus or the reception apparatus,or the restrictions defined by the standards, the minimum value may alsobe restricted to a greater number of bytes (for example, 20 bytes).Similarly, the maximum value of the TLV packet size can be restricted insome cases.

For example, when the minimum value of the TLV packet is X_min bytes,the maximum value is X_max bytes, and the remaining bytes up to theframe boundary after the packet TLV #(n−1) has been placed is Y bytes, aNULL packet cannot be placed when Y<X_min. For example, when X_min is 4bytes, a NULL packet cannot be placed when the remaining bytes is lessthan 4 bytes.

The following describes the method according to the present exemplaryembodiment.

In the present exemplary embodiment, in the operation of sequentiallyplacing TLV packets into a transfer frame and placing a NULL packet inthe end, the remaining bytes up to a frame boundary and the numbers ofbytes of at least two or more TLV packets to be stored are considered inadvance so that the NULL packet is placed appropriately.

For example, a NULL packet is placed according to the following rules.

FIG. 47 is a diagram for illustrating the transmission method accordingto the present exemplary embodiment. In the relative stream of theframe, it is assumed that the remaining bytes up to the frame boundaryis Y, the minimum packet size of the TLV packet is X_min bytes, themaximum packet size of the TLV packet is X_max bytes, the size of theTLV packet (TLV #i) to be placed is X_i bytes, and the size of the nextTLV packet (TLV #(i+1)) is X_(i+1). FIG. 48 is a flowchart showing theoperation performed by the transmission apparatus according to thepresent exemplary embodiment.

First, the transmission apparatus considers a placement of TLV #i thatis a current TLV packet to be processed, into a frame (S301). Next, thetransmission apparatus judges whether or not TLV #(i+1) that is the TLVpacket following TLV #i can be placed into the frame (S302).Specifically, the transmission apparatus judges whether the total sizeof TLV #i and TLV #(i+1) is smaller than the remaining bytes. In otherwords, the transmission apparatus judges whether X_i+X (i+1)<Y issatisfied.

In the case where TLV #(i+1) can be placed into the frame (Yes in S302),the transmission apparatus places TLV #i into the frame (S303), as shownin (1) in FIG. 47. Next, the transmission apparatus selects TLV #(i+1)following TLV #i (S304) and performs the processing of Step S301 and thesubsequent processing for the selected TLV #(i+1). In this case, i ineach processing is incremented by 1.

In contrast, in the case where TLV #(i+1) cannot be placed into theframe (No in S302), the transmission apparatus determines to place aNULL packet into the remaining area (S305).

Next, the transmission apparatus judges whether the remaining area afterthe placement of TLV #i is greater than the minimum value of the TLVpacket (S306). Namely, the transmission apparatus judges whetherY-X_i>X_min is satisfied.

In the case where the remaining area after the placement of TLV #i isgreater than the minimum value of the TLV packet (Yes in S306), thetransmission apparatus places TLV #i into the frame, generates a NULLpacket with the size Y−X _i, places the generated NULL packet after TLV#i in the frame (S307), and completes the placement of the TLV packetinto the frame (S308), as shown in (2) in FIG. 47.

In contrast, in the case where the remaining area after the placement ofTLV #i is smaller than the minimum value of the TLV packet (No in S306),the transmission apparatus does not place the packet TLV #i but places aNULL packet of Y bytes into the frame (S309), as shown in (3) in FIG.47, and completes the placement of the TLV packet into the frame (S308).

Note that, although not shown in FIG. 48, in the case where Y>X_max issatisfied, the transmission apparatus may place two or more NULL packetsinto the frame, as shown in (4) in FIG. 47.

As has been described above, in the case where a minimum value of avariable-length NULL packet size is restricted when variable-length TLVpackets are stored into a fixed-length data area (or the number ofslots), in a frame, which is defined for each relative stream, thetransmission apparatus according to the present exemplary embodimentalways monitors, for instance, the numbers of bytes of at least twovariable-length TLV packets and the remaining bytes up to a frameboundary. Thus, the final TLV packet can be adjusted to coincide withthe frame boundary.

Note that the example in FIG. 47 illustrates the method for placing aTLV packet after considering in advance the remaining bytes up to aframe boundary and the numbers of bytes of the two TLV packets to beplaced. However, the transmission apparatus may place a NULL packetafter considering the numbers of bytes of three or more TLV packets.

In addition, in the example in FIG. 47, the transmission apparatusjudges whether it is the end of a frame in Step S302, and in the casewhere it is the end of a frame (No in S302), the transmission apparatusplaces a NULL packet only or both the packet TLV #i and a NULL packetaccording to whether the remaining area after the placement of TLV #i isgreater than the minimum value of the TLV packet. However, in the caseof not judging in advance whether it is the end of a frame, thetransmission apparatus can place a NULL packet after considering thenumber of bytes of only one TLV packet (TLV #i).

For example, in the case where: (1) the size of TLV #i is smaller thanthe remaining bytes Y; and (2) the remaining area Y-Xi after theplacement of TLV #i is greater than the minimum value of the TLV packet,the transmission apparatus may place TLV #i, and in the case where atleast one of (1) and (2) is not satisfied, the transmission apparatusmay not place the packet TLV #i but place a NULL packet.

Note that, as shown in FIG. 47, by judging in advance whether it is theend of a frame, the amount of processing performed by the transmissionapparatus can be reduced because the occurrence frequency of theprocessing in Step S305 and the subsequent processing can be lowered.

Moreover, as is apparent from FIG. 46 and so on, the TLV packet that hasnot been placed into a target frame is placed into the next frame in theframe boundary. Specifically, this TLV packet is placed immediatelyafter the TLV packet that contains the reference clock information ofthe next frame.

The following describes a variation of the present exemplary embodiment.

The transmission apparatus may perform padding instead of placing afinal TLV packet to coincide with a frame boundary. Here, in the casewhere a TLV packet that contains reference clock information is storedin a head of the first slot of each relative stream of a transfer frame,it is obvious that the TLV packet is not placed across the frames.Therefore, it is defined that padding is performed onto an area from thelast pointer value (the value obtained by adding 1 to the final byte ofa final TLV packet) up to a frame boundary. In this case, the receptionapparatus can determine, by the last pointer value, the number of bytesrequired for padding.

Moreover, as shown in FIG. 49, the transmission apparatus may place,into a transfer slot, a TLV packet that does not contain reference clockinformation beyond (across) reference clock information while placingthe TLV packet that always contains reference clock information into ahead of the first slot of each relative stream.

In FIG. 49, TLV #n is placed across the frames. In addition, TLV #n isplaced across the TLV packet that contains reference clock information.In this case, the location and the size of the TLV packet that containsreference clock information are already known. Therefore, the toppointer value may indicate the byte obtained by adding 1 to the finalbyte of the TLV packet that contains reference clock information or mayindicate the first byte of a TLV packet other than the TLV packet thatcontains reference clock information, instead of the first byte (=0) ofthe TLV packet that contains reference clock information.

Moreover, up to 16 relative streams are stored in a transfer frame and aTLV packet that contains reference clock information is placed in eachof the relative streams. In the case where a reference clock that iscommon to plural relative streams is provided, the same information isalways stored in a head of each relative stream of the frame.

Therefore, in the case of judging that the reference clock is provided,a demodulator of the reception apparatus judges that the respectivereference clocks indicate the same bit (value), and performs theprocessing of averaging the bits. This can improve the ability tocorrect errors.

Moreover, in the case where the data that is the same as the referenceclock information stored in the TLV packet is stored in the area for theTMCC control information, the reception apparatus judges that thereference clock information of the TMCC control information and thereference clock information of the TLV packet indicate the same bit, andperforms the same processing as described above. This can improve theability to correct errors.

Furthermore, because the reception quality of the TMCC controlinformation is high, the reception apparatus may replace the referenceclock information of the TLV packet with the reference clock informationof the TMCC control information.

In such case, in order to improve the error correction ability, thereference clock information of the TMCC control information and thereference clock information of the TLV packet that contains referenceclock information need to indicate the same bit. Therefore, scramblingor power spread may not be performed onto the TLV packet that containsreference clock information. Scrambling sequence may be identically setfor each relative stream and the TLV packet that contains referenceclock information may be scrambled with the same scrambling sequence.

Sixth Exemplary Embodiment

The present exemplary embodiment describes the methods for shorteningthe processing delay in channel selection.

In the first method, the reception apparatus starts filtering IP dataflows without using full headers. In order to enable the receptionapparatus to start such a filtering, CIDs respectively corresponding toeach of the IP data flows are previously set. Alternatively, theinformation for the reception apparatus to specify CID(s) istransmitted.

At the same time when a desired service is specified through the channelselection operation by a viewer, the reception apparatus receives anAMT, and determines the IP data flow of the desired service and the CIDcorresponding to the IP data flow, based on the information in the AMT.When having determined the CID, the reception apparatus can perform thefiltering of the IP data flows, and thus the processing delay in channelselection can be shortened. In addition, the amount of receptionprocessing can be reduced.

In the second method, in the case where a TLV stream includes one IPdata flow transferring MMT packets (also referred to as MMTP packets)and a total of two IP data flows including this IP data flow and an IPdata flow transferring NTP packets are included in the TLV stream, it isdefined that header compression is always performed on the IP data flowtransferring MMT packets and is always not performed on the IP data flowtransferring NTP packets.

The reception apparatus performs, using a data type in a TLV packet, thefiltering of the IP data flows based on whether or not the header of anIP packet has been compressed. Thus, the filtering of the IP data flowsbecomes unnecessary, and the processing delay in channel selection canbe shortened. In addition, the amount of reception processing can bereduced.

First, the details of the IP packets and IP header compression (HCfB:Header Compression for Broadcasting) defined in the ARIB STD-B32 will bedescribed with reference to FIG. 50.

As has been described with reference to FIG. 2, a TLV packet can storean IPv4 packet, an IPv6 packet, a compressed IP packet, and so on.Moreover, the type of the IP packet stored in the TLV packet isidentified using the data type included in the header of the TLV packet.The compressed IP packet has a header structure which differs accordingto a context identification header type (hereinafter referred to as CIDtype).

CID type=0x20 indicates that a header of the compressed IP packet is apartial IPv4 header and has a context identifier (hereinafter referredto as CID), a header excluding a part of the fields in the IPv4 packetheader, and so on. The partial IPv4 header includes IP data flowspecification information. The IP data flow specification informationindicates a destination IP address, a source IP address, a destinationport number, a source port number, and a protocol type, and in the caseof IPv6 header, a next header is indicated instead of the protocol type.Note that, in FIG. 50, the header information indicated by the hatchingin dots includes the IP data flow specification information. The CID isan identifier for identifying the same IP data flows, and the same CIDis allocated for the compressed IP packets having the same IP data flowspecification information.

CID type=0x21 indicates that the header includes a CID andidentification field in the IPv4 header, but does not include the IPdata flow specification information.

CID type=0x60 indicates that the header has a CID and a header excludinga part of the fields in the IPv6 header, and also includes the IP dataflow specification information.

CID type=0x61 indicates that the header includes only a CID and does notinclude an IP header. This CID type is normally used for the IPv6packets only, but may also be used for the IPv4 packets. Hereinafter,the description will be provided under the assumption that this CID typeis used only for the IPv6 packets.

Note that a 4-bit sequence number and a CID type are indicated in all ofthe CID-typed headers of the compressed IP packets, although not shownin the diagram. Moreover, a header that includes the IP data flowspecification information (CID type=0x20 or 0x60) is referred to as fullheader whereas a header that does not include the IP data flowspecification information (CID type=0x21 or 0x61) is referred to ascompressed header.

Although a part of the fields in some of the IP packets is excluded froma full header, the reception apparatus can reconfigure the IP header (IPheader extension) of the same packets for completion based on theinformation in the TLV header, and the like. On the contrary, acompressed header does not include the IP data flow specificationinformation, and thus with a single packet, the IP header extensioncannot be realized. The reception apparatus obtains necessaryinformation based on the header information of the full header havingthe same CID as that of the compressed header, for example.

FIG. 51 is a diagram showing a method of multiplexing compressedpackets. This is an example of compressing the headers of the IPv6packets of the same IP data flow, and in the TLV packet header that isnot shown in the diagram, the data type indicating that the TLV packetis a compressed IP packet is indicated. In the case of compressing theheaders of the IPv6 packets, either of CID type=0x60 or CID type=0x61 isused. As these packets belong to the same IP data flow, the same valueis indicated in the respective CIDs. Note that the following descriptionprovides an example of the IPv6 packets; however, the same applies tothe case of the IPv4 packets.

In the example shown in FIG. 51, a full header is transmitted once everythree packets and a compressed header is transmitted for the remainingtwo packets. Thus, by regularly inserting a full header and compressingthe remaining headers, overhead of headers can be reduced.

After having received a full header, the reception apparatus extends thefull header based on the information in the TLV header, and the like. Inaddition, since a compressed header needs to be extended together with afull header, the reception apparatus extends the compressed header afterthe reception of the full header having the same CID as that of thecompressed header. Moreover, after the header extension, the receptionapparatus performs the filtering of the IP packets or UDP packets basedon the IP data flow specification information.

Note that the header extension is not necessarily required and animplementation method without the header extension has also beenconsidered. In such case, with the filtering using the CIDs, theoperation equivalent to the filtering of the IP packets or UDP packetscan be performed. In this case, the reception apparatus separatelycreates a correspondence table in which the IP data flow specificationinformation and a CID are associated with each other, and filters thepackets each having the CID corresponding to a desired IP data flow.

However, such a method requires some solutions for the followingproblems. In a TLV stream, plural IP data flows are included, and an IPdata flow transferring NTP packets and an IP data flow transferring MMTpackets are included at least. The number of the IP data flowstransferring MMT packets may be one or plural depending on the case.Furthermore, an IP data flow exclusively used for transferring MMT-SIthat is control information may be included in the TLV stream, in somecases.

When extracting a desired IP data flow from a TLV stream, the receptionapparatus performs filtering of IP data flows or filtering of IP packetsor UDP packets. In addition, when filtering the IP data flows, thereception apparatus needs to specify the IP data flow of a desiredservice and identify the packets that belong to the desired IP dataflow.

However, the reception apparatus can identify the packets that belong tothe desired IP data flow only after the reception of a full header. Thismight delay the processing until the reception apparatus firstlyreceives a full header, and thus the processing delay in channelselection gets longer. Furthermore, in the case where the transmissionintervals of the full headers are long, the processing delay in channelselection gets even longer. For example, when the transmission intervalsof the full headers are N seconds, the processing delay in channelselection gets longer by N seconds at the most.

The following describes the first method for shortening the processingdelay in channel selection. The reception apparatus starts filtering IPdata flows without using full headers. In order to enable the receptionapparatus to start such a filtering, CIDs corresponding to each of theIP data flows are previously set.

For example, fixed values are previously set for the CIDs according tothe type of the IP data flow, as follows: the IP data flow of the NTP isset as CID=0; the IP data flow of service 1 is set as CID=1; the IP dataflow of service 2 is set as CID=2; the IP data flow of service 3 is setas CID=3; and the IP data flow exclusively used for SI is set as CID=20,etc.

In the case where plural services are included in a TLV stream,regularity is defined so that the correspondence between a service IDand a CID can be uniquely determined. For example, by setting the low Nbits of a service ID to the same value as the value indicated by a CID,the service ID can be associated with the CID.

This enables the reception apparatus to determine the CID of a desiredIP data flow at the same time when the desired IP data flow is specifiedthrough the channel selection operation by the viewer. Thus, the IP dataflow specification information becomes unnecessary and the receptionapparatus can start the filtering of the IP data flows without waitingfor the reception of a full header. Accordingly, the processing delay inchannel selection can be shortened.

Note that the following method may be used as an alternative method.Instead of previously determining the CIDs corresponding to each of theIP data flows, the information indicating the correspondence between anIP data flow and a CID may be multiplexed onto a broadcast signal andthen transferred, for instance. It is desirable, for example, to includethis information into the control information that can be processedbefore the start of the filtering of the IP data flows. This informationis stored, for example, into an address map table (AMT) which istransfer control information stored in a TLV packet. As an alternativeexample, the control information as such that can be processed beforethe start of the filtering of the IP data flows may be stored into a PLTor an MPT which is MMT-SI, or the like.

The AMT is a table for storing a destination IP address and a source IPaddress for each service. The AMT does not include a destination portnumber, a source port number, a protocol type, etc., therefore, thereception apparatus cannot specify an IP data flow that corresponds toeach service, using the AMT. Nevertheless, by setting the port numbersand the protocol type to known values, it is possible to make use of theAMT as the information for specifying an IP data flow. Alternatively,private_data_byte area included in the AMT may be extended so that theport numbers and the protocol type can be specified.

In the case of using the AMT as a table for specifying the IP data flowwith respect to a service, with the method as described above, theinformation indicating a CID corresponding to an IP data flow is furtherincluded into a signal. For example, the CID corresponding to the IPdata flow is indicated in private_data_byte included in the AMT.

At the same time when a desired service is specified through the channelselection operation by the viewer, the reception apparatus receives anAMT, and specifies the IP data flow and the CID which correspond to thedesired service, based on the information in the AMT. When havingspecified the CID, the reception apparatus can perform the filtering ofthe IP data flows, and thus the processing delay in channel selectioncan be shortened. Moreover, the amount of reception processing can bereduced.

Note that in the case of using the above-described method, full headersmay not necessarily be transmitted and only compressed IP packets may betransferred. In this case, further effect of header compression can begained.

Note that the AMT is a table indicating information per service,therefore, such AMT can indicate neither the information on the IP dataflow exclusively used for SI (MMT-SI) nor the information on the IP dataflow transferring NTP packets. Therefore, the CID of the IP data flowexclusively used for SI or the CID of the IP data flow transferring NTPpackets may be set to a fixed value that is previously defined, and theCID corresponding to each service may be indicated in the AMT.Alternatively, the AMT may be extended so that the CIDs other than thoseassociated with the respective services can be specified.

Note that in the case where the number of services included in a TLVstream is not plural, the IP data flow specification information and theCIDs may not necessarily be indicated in the AMT.

Furthermore, the reception apparatus may perform the channel selectionoperation without using full headers only in the case where the IP dataflow specification information and the CIDs are described in the AMT.

Next, the second method of shortening the processing delay in channelselection will be described.

In the second method, the number of IP data flows transferring MMTpackets in a TLV stream is limited to one. The case where the IP dataflow transferring NTP packets and the IP data flow transferring MMTpackets are stored one for each and the IP data flow exclusively usedfor SI is not stored in the TLV stream will be described below.

In this case, the processing delay in channel selection can be shortenedeven with the use of the first method; however, with the methodindicated below, the reception apparatus can start IP filtering earlieralthough the information for specifying IP data flow and CID is nottransmitted.

In the case where the number of the IP data flows transferring MMTpackets in a TLV stream is one, a total of two IP data flows includingthis IP data flow and an IP data flow transferring NTP packets areincluded in the TLV stream. Here, it shall be defined that headercompression is always performed on the IP data flow transferring MMTpackets and is always not performed on the IP data flow transferring NTPpackets.

It is possible to restrain jitter fluctuation by not performing theheader compression on the IP data flow transferring NTP packets.Moreover, by always performing the header compression on the IP dataflow transferring MMT packets, the effect of reducing the overhead canbe enhanced.

The reception apparatus determines whether or not the header of an IPpacket has been compressed, using the data type in the TLV packet, andperforms the filtering of the IP data flows based on the determinationresult.

More specifically, in the case where the header of the IP packet hasbeen compressed (data type=header compressed packet), the receptionapparatus determines that the IP packet belongs to the IP data flowtransferring MMT packets.

In the case where the header of the IP packet has not been compressed(data type=IPv4 packet or IPv6 packet), the reception apparatusdetermines that the IP packet belongs to the IP data flow transferringNTP packets.

With the processing as described above, the IP header extension, thefiltering using the IP addresses or UDP addresses, the filtering usingthe CIDs, and the like are unnecessary, and thus the reception apparatuscan reduce the delay that occurs until the reception of a full header.Moreover, without the use of the AMT, the delay until the reception ofthe AMT can be shortened. Furthermore, the amount of receptionprocessing can also be reduced.

Note that in the case of using the above-described method, full headersmay not necessarily be transmitted and only compressed IP packets may betransferred. In this case, further effect of header compression can begained.

Moreover, the reception apparatus can separately obtain a full headerand analyze the IP data flow specification information.

The following describes other variations.

(1) Even in the case where plural services are included and an IP dataflow exclusively used for SI is stored in a TLV stream, it may bedefined that header compression is always performed on the IP data flowtransferring MMT packets and is always not performed on the IP data flowtransferring NTP packets. Even in this case, the reception apparatus candetermine that the TLV packet that is not subjected to the headercompression is an NTP packet. Thus, the filtering of the IP data flowthat includes NTP packets becomes unnecessary, which enables thereduction in the amount of reception processing and also the shorteningof the time to start the processing such as a clock reproduction usingthe NTP packets, and so on.

(2) In the case where the reception apparatus has a memory with asufficient capacity, it is possible to shorten the processing delay inchannel selection without using the first and second methods forshortening the processing delay in channel selection.

The reception apparatus starts filtering IP data flows based on the CIDsin the state where it is before the reception of a full header and adesired IP data flow cannot be specified, for instance. Here, thereception apparatus accumulates all the data that has been filtered.After that, the reception apparatus receives a fill header, specifies adesired IP data flow, and specifies the CID corresponding to the desiredIP data flow. Then, after that, the reception apparatus discards thedata other than the data that has the specified CID from among theaccumulated data, and performs high-speed processing of the data havingthe specified CID. Thus, it is possible to shorten the processing delayin channel selection.

(3) It may be defined that only the IP data exclusively used for SI outof the IP data flow transferring MMT packets is not subjected to headercompression.

In the case where the data type in a TLV packet header indicates aheader compressed packet, the reception apparatus determines that the IPpacket belongs to the IP data flow transferring MMT packets, excludingthe IP data flow exclusively used for SI. In the case where the datatype in the TLV packet header indicates an IPv4 packet or an IPv6 packet(in the case where the header of an IP packet is not compressed), thereception apparatus determines that the IP packet belongs to the IP dataflow transferring NTP packets or the IP data flow exclusively used forSI.

Moreover, in the case where the IP data flow specification informationis previously determined for the IP data flow transferring NTP packetsand for the IP data flow transferring MMT packets that is exclusivelyused for SI, the reception apparatus can determine, at the same timewhen the TLV packet header is filtered and also based on the IP dataflow specification information, whether the IP data flow is the onetransferring NTP packets or the one exclusively used for SI.

In the description so far, the case where the reception apparatussequentially receives the TLV packets of a TLV stream has been describedas an example.

The case where the TLV packets of the TLV stream are sequentiallyreceived is, for example, the case where the reception apparatussequentially inputs, as TLV packets and for the TLV packet processing,the TLV packets obtained in a transfer layer.

In the transfer layer, one or more TLV streams and plural TLV packetsare stored in one transfer frame. The reception apparatus receives theplural TLV packets at a burst in the transfer layer processing. Afterhaving received the TLV packets per TLV stream in the transfer layer,the reception apparatus performs IP header compression and extension ofa desired TLV stream.

In the case where the full IP packets that have not been compressed andhave been obtained through the above-described processing aresequentially input for the IP packet processing, when the IP data flowin the TLV stream included in the transfer frame includes at least oneor more TLV packets each having a full header, the reception apparatuscan perform header extension onto all the IP data flows in one transferframe.

In order to realize the abovementioned processing, it is defined that atleast one or more full headers shall be transferred with respect to theIP data flow in the TLV stream included in the transfer frame. Thisenables the reception apparatus to perform header extension at one timein the transfer layer. Therefore, the reception apparatus does not needto await the header extension or the reception of a full header in thesubsequent processing, and thus the processing delay in channelselection can be shortened.

Moreover, by previously determining the location of the TLV packet thatincludes a full header in the TLV stream of the transfer frame, thereception apparatus can easily obtain the full header. For example, itis defined that the TLV packet positioned at the head in the TLV streamincluded in the transfer frame always has a full header. Note that itmay be defined that in the case where a head TLV packet in the TLVstream is always an NTP packet, the second TLV packet always has a fullheader. Alternatively, other rules may be defined.

The following describes a flow of the processing performed by thereception apparatus. FIG. 52 is a flowchart showing the receptionprocessing performed by the reception apparatus using theabove-described first method (CIDs are previously set).

First, the reception apparatus analyzes an AMT and determines whether ornot the CIDs are previously set (S401). In the case where the CIDs arepreviously set and a desired IP data flow can be specified (Yes inS402), the reception apparatus obtains the CID of the desired IP dataflow using the AMT and starts the filtering of the IP data flows beforethe reception of a full header (S403).

On the contrary, in the case where the CIDs are not previously set (Noin S402), the reception apparatus specifies the desired IP data flowafter having received a full header and starts the filtering of the IPdata flow (S404).

FIG. 53 is a flowchart showing the reception processing performed by thereception apparatus using the above-described second method (headercompression is always performed on the IP data flow transferring MMTpackets and is always not performed on the IP data flow transferring NTPpackets).

First, the reception apparatus analyzes the data type in a TLV packetand determines whether or not the header of the IP packet stored in theTLV packet has been compressed (S411). In the case where the header ofthe IP packet has been compressed (Yes in S412), the reception apparatusdetermines that the IP packet belongs to the IP data flow transferringMMT packets (S413). On the contrary, in the case where the header of theIP packet has not been compressed (No in S412), the reception apparatusdetermines that the IP packet belongs to the IP data flow transferringNTP packets (S414).

Note that, in the processing of a TLV stream, the analysis on the IPdata flows using compressed IP headers or IP packet headers isunnecessary.

As has been described above, the transmission apparatus according to thepresent exemplary embodiment transmits content through broadcasting.FIG. 54 is a block diagram showing transmission apparatus 70 accordingto the present exemplary embodiment. Transmission apparatus 70 includesgenerator 71 and transmitter 72.

FIG. 55 is a flowchart showing the transmission method employed bytransmission apparatus 70 according to the present exemplary embodiment.

First, generator 71 generates a frame for transfer (transfer frame)which stores the first IP packets in which content (e.g., MMT packets)is stored and the second IP packets each including reference clockinformation (e.g., NTP) indicating a time for the playback of thecontent (S421). More specifically, generator 71 performs headercompression on the first IP packets and does not perform it on thesecond IP packets.

To be more specific, as shown in FIGS. 50 and 51, generator 71 attaches,as the header compression processing, the following: a full header whichincludes the specification information for specifying the IP data flowto which one or more first IP packets belong, to a part of the one ormore first IP packets; and a compressed header which does not includethe specification information to the first IP packet other than the partof the one or more first IP packets.

Next, transmitter 72 transmits the frame generated by generator 71(S422).

As has been described above, the reception apparatus according to thepresent exemplary embodiment receives the content through broadcasting.FIG. 56 is a block diagram showing reception apparatus 80 according tothe present exemplary embodiment. Reception apparatus 80 includesreceiver 81, determiner 82, and playback unit 83.

FIG. 57 is a flowchart showing the reception method employed byreception apparatus 80 according to the present exemplary embodiment.First, receiver 81 receives a frame for transfer (transfer frame) whichstores: the first IP packets storing content (e.g., MMT packets), whoseheaders have been compressed; and the second IP packets, each of whichincludes the reference clock information (e.g., NTP) indicating a timefor the playback of the content and whose headers have not beencompressed (S431).

Next, determiner 82 determines whether the IP packet is the first IPpacket or the second IP packet based on whether or not the header of theIP packet has been compressed (S432). To be more specific, a full headerwhich includes the specification information for specifying the IP dataflow to which one or more first IP packets belong is attached to a partof the one or more first IP packets; and a compressed header which doesnot include the specification information is attached to the first IPpacket other than the part of the one or more first IP packets, as theheader compression processing, as shown in FIGS. 50 and 51. Moreover,determiner 82 determines the IP packet whose header has been compressedto be the first IP packet and determines the IP packet whose header hasnot been compressed to be the second IP packet.

Next, playback unit 83 plays back the content stored in the first IPpackets using the reference clock information stored in the respectivesecond IP packets, based on the determination result.

As shown in FIG. 50, whether or not the IP header has been compressed isindicated in the information (data type) included in the header of theTLV packet.

In other words, in Step S421, generator 71 stores the informationindicating that the header of the first IP packet has been compressed,into the header of the TLV packet in which the first IP packet isstored, and stores the information indicating that the header of thesecond IP packet has not been compressed, into the header of the TLVpacket in which the second IP packet is stored.

In Step S432, determiner 82 determines whether the IP packet stored inthe TLV packet is the first IP packet or the second IP packet based onthe information stored in the header of the TLV packet.

With the processing as described above, the reception apparatus canfilter the IP data flows based on whether or not the header compressionhas been performed. Thus, it is possible to shorten the processing delayin channel selection.

The following is included as various exemplary embodiments according tothe present disclosure.

The transmission method according to the first disclosure includes:generating a frame for transfer in which one or more first internetprotocol (IP) packets and one or more second IP packets are stored, theone or more first IP packets storing content, and each of the one ormore second IP packets including reference clock information whichindicates a time for playing back the content; and transmitting thegenerated frame through broadcasting. In the generating, headercompression is performed on the one or more first IP packets and theheader compression is not performed on the one or more second IPpackets.

The transmission method according to the second disclosure is thetransmission method according to the first disclosure, and the headercompression includes: (i) attaching, to a part of the one or more firstIP packets, a full header which includes specification information forspecifying an IP data flow to which the one or more first IP packetsbelong; and (ii) attaching, to a first IP packet other than the part ofthe one or more first IP packets, a compressed header which does notinclude the specification information.

The transmission method according to the third disclosure is thetransmission method according to the first disclosure, and the referenceclock information complies with a network time protocol (NTP).

The transmission method according to the fourth disclosure is thetransmission method according to the first disclosure, and the contentis stored in an MPEG media transport (MMT) packet in each of the one ormore first IP packets.

The transmission method according to the fifth disclosure is thetransmission method according to the first disclosure, and the frameincludes one or more second transfer units, each having a fixed length,each of the one or more second transfer units includes one or more firsttransfer units, and each of the one or more first transfer unitsincludes one of the one or more first IP packets; and the one or moresecond IP packets.

The transmission method according to the sixth disclosure is thetransmission method according to the fifth disclosure, and each of theone or more first transfer units is a type length value (TLV) packet,each of the one or more second transfer units is a slot defined under atransmission system for advanced wide band satellite digitalbroadcasting, and the frame is a transfer slot defined under thetransmission system for advanced wide band satellite digitalbroadcasting.

The reception method according to the seventh disclosure includes:receiving, through broadcasting, a frame for transfer in which one ormore internet protocol (IP) packets are stored, the one or more IPpackets storing content and including: one or more first IP packetswhose headers have been compressed; and one or more second IP packetswhose headers have not been compressed, each of the one or more secondIP packets including reference clock information which indicates a timefor playing back the content; determining whether each of the one ormore IP packets that are received is the first IP packet or the secondIP packet based on whether or not a header of the IP packet has beencompressed; and playing back the content stored in the one or more firstIP packets, using the reference clock information stored in the each ofthe one or more second IP packets, based on a result of thedetermination.

The reception method according to the eighth disclosure is the receptionmethod according to the seventh disclosure, and the header compressionincludes: (i) attaching, to a part of the one or more first IP packets,a full header which includes specification information for specifying anIP data flow to which the one or more first IP packets belong; and (ii)attaching, to a first IP packet other than the part of the one or morefirst IP packets, a compressed header which does not include thespecification information.

The reception method according to the ninth disclosure is the receptionmethod according to the seventh disclosure, and the reference clockinformation complies with a network time protocol (NTP).

The reception method according to the tenth disclosure is thetransmission method according to the seventh disclosure, and the contentis stored in an MPEG media transport (MMT) packet in each of the one ormore first IP packets.

The reception method according to the eleventh disclosure is thereception method according to the seventh disclosure, and the frameincludes one or more second transfer units, each having a fixed length,each of the one or more second transfer units includes one or more firsttransfer units, and each of the one or more first transfer unitsincludes one of: the one or more first IP packets; and the one or moresecond IP packets.

The reception method according to the twelfth disclosure is thetransmission method according to the eleventh disclosure, and each ofthe one or more first transfer units is a type length value (TLV)packet, each of the one or more second transfer units is a slot definedunder a transmission system for advanced wide band satellite digitalbroadcasting, and the frame is a transfer slot defined under thetransmission system for advanced wide band satellite digitalbroadcasting.

The transmission apparatus according to the thirteenth disclosureincludes: a generator which generates a frame for transfer in which oneor more first internet protocol (IP) packets and one or more second IPpackets are stored, the one or more first IP packets storing content,and each of the one or more second IP packets including reference clockinformation which indicates a time for playing back the content; and atransmitter which transmits the generated frame through broadcasting.The generator performs header compression on the one or more first IPpackets and does not perform the header compression on the one or moresecond IP packets.

The reception apparatus according to the fourteenth disclosure includes:a receiver which receives, through broadcasting, a frame for transfer inwhich one or more internet protocol (IP) packets are stored, the one ormore IP packets storing content and including: one or more first IPpackets whose headers have been compressed; and one or more second IPpackets whose headers have not been compressed, each of the one or moresecond IP packets including reference clock information which indicatesa time for playing back the content; a determiner which determineswhether each of the one or more IP packets that are received is thefirst IP packet or the second IP packet based on whether or not a headerof the IP packet has been compressed; and a playback unit which playsback the content stored in the one or more first IP packets, using thereference clock information stored in the each of the one or more secondIP packets, based on a result of the determination.

Note that in the aforementioned exemplary embodiments, components mayeach include dedicated hardware or may be implemented through executionof a software program suitable for each component. The components may beeach implemented by a program execution unit, such as a CPU and aprocessor, reading and executing the software program recorded in arecording medium such as a hard disk and a semiconductor memory.

In addition, the components may be circuits. These circuits mayconstitute one circuit as a whole, or may be different circuits. Inaddition, each of these circuits may be a general-purpose circuit, ormay be a dedicated circuit.

For example, in each of the aforementioned exemplary embodiments,processes executed by a specific processor may be executed by anotherprocessor. In addition, order of the plurality of processes may bechanged, and the plurality of processes may be executed in parallel.

Moreover, each of the functional blocks used for the descriptions ofeach of the above-described exemplary embodiments are typically realizedas an LSI which is an integrated circuit having an input terminal and anoutput terminal. These functional blocks may be individually integratedinto one chip or may be integrated into one chip so as to include a partor all of the functional blocks. Although LSI is mentioned here, it mayalso be referred to as IC, system LSI, super LSI, or ultra LSI dependingon the difference in the degree of integration.

Moreover, the ways to achieve integration are not limited to the LSI,and the integration may be realized using a dedicated communicationcircuit or a general-purpose processor. A field programmable gate array(FPGA) which is programmable after the manufacturing of LSIs or areconfigurable processor which can reconfigure the connection orconfiguration of the circuit cells in an LSI may be used for theintegration.

Furthermore, with the advancement in semiconductor technology or adifferent technology deriving from the semiconductor technology, abrand-new technology may replace the LSIs. In that case, the functionalblocks may be naturally integrated using such a technology. Onepossibility is an application of biotechnology.

The reception apparatus (reception method) and transmission apparatus(transmission method) according to one or more aspects have beendescribed above based on the exemplary embodiments. However, the presentdisclosure is not limited to these exemplary embodiments. The presentexemplary embodiments to which various modifications conceivable by aperson skilled in the art are made and aspects that are made bycombining elements of different exemplary embodiments may also be withinthe scope of the one or more aspects as long as such aspects do notdepart from the gist of the present disclosure.

Although only some exemplary embodiments of the present disclosure havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure.

INDUSTRIAL APPLICABILITY

The transmission method and the reception method according to thepresent disclosure are applicable to the broadcasting system in which anMMT scheme is used.

What is claimed is:
 1. A transmission method comprising: generating aframe for transfer which includes one or more first internet protocol(IP) packets and one or more second IP packets, the one or more first IPpackets storing content, and each of the one or more second IP packetsincluding first reference clock information which indicates a time forplaying back the content; and transmitting the generated frame throughbroadcasting including attaching, to each of the one or more first IPpackets and each of the one or more second IP packets, a contextidentifier indicating a preset fixed value in accordance with a type ofdata stored in the one or more first IP packets or the one or moresecond IP packets.
 2. The transmission method according to claim 1,wherein in the generating, a header compression is performed on the oneor more first IP packets and includes: (i) attaching, to a part of theone or more first IP packets, a full header which includes specificationinformation for specifying an IP data flow to which the one or morefirst IP packets belong; and (ii) attaching, to a first IP packet otherthan the part of the one or more first IP packets, a compressed headerwhich does not include the specification information.
 3. Thetransmission method according to claim 1, wherein the first referenceclock information complies with a network time protocol (NTP).
 4. Thetransmission method according to claim 1, wherein the content is storedin an MPEG media transport (MMT) packet in each of the one or more firstIP packets.
 5. The transmission method according to claim 1, wherein theframe includes one or more second transfer units, each having a fixedlength, each of the one or more second transfer units includes one ormore first transfer units, and each of the one or more first transferunits includes one of the one or more first IP packets; and the one ormore second IP packets.
 6. The transmission method according to claim 5,wherein each of the one or more first transfer units is a type lengthvalue (TLV) packet, each of the one or more second transfer units is aslot defined under a transmission system for advanced wide bandsatellite digital broadcasting, and the frame is a transfer slot definedunder the transmission system for advanced wide band satellite digitalbroadcasting.
 7. A reception method comprising; receiving, throughbroadcasting, a frame for transfer which includes one or more firstinternet protocol (IP) packets and one or more second IP packets, theone or more first IP packets storing content, and each of the one ormore second IP packets including first reference clock information whichindicates a time for playing back the content; determining whether eachof the one or more IP packets that are received is the first IP packetor the second IP packet, and a type of data stored in the one or morefirst IP packets or the one or more second IP packets according to apreset fixed value indicated in a context identifier attached to each ofthe one or more first IP packets and each of the one or more second IPpackets; and playing back the content stored in the one or more first IPpackets, using the first reference clock information stored in the eachof the one or more second IP packets, based on a result of thedetermination.
 8. The reception method according to claim 7, wherein inthe determining, it is determined whether or not compression isperformed on an IP packet, the header compression includes; (i)attaching, to a part of the one or more first IP packets, a full headerwhich includes specification information for specifying an IP data flowto which the one or more first IP packets belong; and (ii) attaching, toa first IP packet other than the part of the one or more first IPpackets, a compressed header which does not include the specificationinformation.
 9. The reception method according to claim 7, wherein thefirst reference clock information complies with a network time protocol(NTP).
 10. The reception method according to claim 7, wherein thecontent is stored in an MPEG media transport (MMT) packet in each of theone or more first IP packets.
 11. The reception method according toclaim 7, wherein the frame includes one or more second transfer units,each having a fixed length, each of the one or more second transferunits includes one or more first transfer units, and each of the one ormore first transfer units includes one of the one or more first IPpackets; and the one or more second IP packets.
 12. The reception methodaccording to claim 11, wherein each of the one or more first transferunits is a type length value (TLV) packet, each of the one or moresecond transfer units is a slot defined under a transmission system foradvanced wide band satellite digital broadcasting, and the frame is atransfer slot defined under the transmission system for advanced wideband satellite digital broadcasting.
 13. A transmission apparatuscomprising: a non-transitory memory configured to store one or moreprograms; and a processor configured to execute the one or more programsand cause the transmission apparatus to operate as: a generator whichgenerates a frame for transfer which includes one or more first internetprotocol (IP) packets and one or more second IP packets, the one or morefirst IP packets storing content, and each of the one or more second IPpackets including first reference clock information which indicates atime for playing back the content; and a transmitter which transmits thegenerated frame through broadcasting including attaching, to each of theone or more first IP packets and each of the one or more second IPpackets, a context identifier indicating a preset fixed value inaccordance with a type of data stored in the one or more first IPpackets or the one or more second IP packets.
 14. A reception apparatuscomprising: a non-transitory memory configured to store one or moreprograms; and a processor configured to execute the one or more programsand cause the reception apparatus to operate as: a receiver whichreceives, through broadcasting, a frame for transfer which includes oneor more first internet protocol (IP) packets and one or more second IPpackets, the one or more first IP packets storing content, and each ofthe one or more second IP packets including first reference clockinformation which indicates a time for playing back the content; adeterminer which determines whether each of the one or more IP packetsthat are received is the first IP packet or the second IP packet, and atype of data stored in the one or more first IP packets or the one ormore second IP packets according to a preset fixed value indicated in acontext identifier attached to each of the one or more first IP packetsand each of the one or more second IP packets; and a playback unit whichplays back the content stored in the one or more first IP packets, usingthe first reference clock information stored in the each of the one ormore second IP packets, based on a result of the determination.
 15. Thetransmission method according to 5, wherein second reference clockinformation is stored in a header of the second transfer unit.
 16. Thereception method according to claim 11, wherein second reference clockinformation is stored in a header of the second transfer unit.